This is late because they just today (4 days later) posted the results.  The race committee was quite surprised to find that the 400 people they anticipated turned out to be 800 so I'm guessing they had some issues with timing as it wasn't chip timed.  Since my official time is within a couple of seconds of what my garmin said, I'll take it.

I PR'd this race by 7 seconds coming in at 25:54, but I am not very happy with the race.  I was plagued once again with side stitches and stomach cramps and actually had to stop twice for about 10 seconds each time during mile 3 so as not to pass out.

Mile 1 felt great.  My legs felt great, my breathing was fine and I was just cruising along.  A faster friend of mine had decided to do this more as a fun run so ran with me from about the start of mile 1.5 until about mile 2, but it was then that the side stitch hit and I waved her ahead.  I was determined to run through the stitch, but it continued to grow in intensity until finally it shifted to my actual stomach (or something like that.  It's hard to explain) and became a full blown stomach cramp.  I really tried to keep going and keep some kind of a decent pace, but I started getting dizzy and around mile 2.5 had to stop and lean over with my head down.  The stomach cramp didn't abate completely, but got more manageable so I continued on.  About mile 2.8, it had intensified again and I had to stop AGAIN.  Argh!  Again, the cramp became manageable and I managed to finish the race.  After I got through the never ending finishing chute, I immediately sat down and put my head between my legs and the cramp finally went away about 5 minutes later.

I am extremely frustrated with this stitch/cramp thing that has hit in every single 5k and 10k I've run in the past year.  My longer race times suggest that I should be able to run a much faster 5k, so I know endurance isn't an issue.  I've been trying to do speedwork to get used to running fast, but you're not supposed to do any of that at race pace, right?

Does anyone have any advice as to where I should go from here?  I should say that I have always had digestive issues throughout my life, so maybe this is something that I'm stuck with, but I hate to think that's the case.  If anyone has had similar experiences or has any advice, I would greatly appreciate hearing it.  Thanks in advance.

I might have mentioned this all before... but it sounds like a diaphragm spasm.   Right below your ribcage, sort of at the top of you stomach?   Have you looked into the book mentioned in this artcle?

http://www.runnersworld.com/running-tips/running-air-breathing-technique

I get the same thing in fast races at about 1.5 miles in, and I don't really have a solution other than I have narrowed it down to being triggered by my breathing.  I try to really concentrate on the techniques mentioned in the article above before it hits and it's been better, but not 100% gone (got another one in my 5k this weekend... grr...).  

Good luck and congrats on the PR!

I've been trying to do speedwork to get used to running fast, but you're not supposed to do any of that at race pace, right?

Actually many plans recommend doing some speedwork at race pace-- 400m repeats or 800m repeats (or even 1000-1200m repeats for faster runners) are a staple 5K workout.

I've dealt with side stitches in 5K races occasionally, mainly early in a given season when I haven't been doing any fast racing.  Maybe some 5K pace running, starting with short repeats (200m) and going up to 800-1000m would help?

You still had a great time, and congrats on the PR.  Given how much you had to stop, you can probably go quite a bit faster if you can get past that issue.

You absolutely can train at faster than 5k race pace, I have spent the entire year doing just that in the form of "R" pace training.  The question is at what pace, when and for how long.

Based on your new PR, your "R" pace is :54 seconds (7:14 pace) for 200 meters, and 1:54 for 400 meters (7:38 pace).  There are a million "R" pace workouts but a couple of simple ones are 4 X 200 + 2 X 400, or 4 X 400 + 4 X 200.

The key to figuring out how many to do is to spend no more than 3 to 5 % of your weekly mileage total running at "R" pace per week.  So for me, I may do 10 to 12 X 400 or some combination that totals no more than 5000 meters (3 miles) at "R" pace in one workout.

As for recoveries, with "R" pace I usually recover the same distance I ran, so my 10 X 400's would be with 400 meter recoveries.

I cannot offer any help with the side stitches other than to say that if you somehow became comfortable running a "R" pace, it may make 5k pace not so bad.

I do a lot of speedwork at various paces.

Strides at the end of a run are done at what would be about 400-800 meter race pace.  Very fast.  5:15 pace

Speed repetitions last from 45 seconds to 2:30 and about mile race pace.  5:30 pace

VO2max intervals last 3-5 minutes about 5K race pace.  6:00 pace

Tempo runs last 3-6 miles at about 6:30 pace

Marathon pace runs last 8-12 miles at about 6:45 pace

My guess is that you are not doing sufficient speedwork for your body to be used to those kinds of efforts.  No, you don't want to go out and run a 5K at 5K race pace but you do want to do something like 6 x 800 @ 5K race pace with 400 recovery jogs.  That gives you 3 miles of hard running but it's not as stressful as a race because you get the recovery with those 400 meter jogs.  Bear in mind that when you first start these, you may not be able to finish the workout with 400 meter recovery jogs.  It may be better to start with 600 meter jogs and then work your way to 400.

How long have you been running? The first year or so I really started racing I would throw up or cramp up every.single.time. Now I don't. Not sure what changed but I think part of it was learning my limits and part of it was perfecting my pre- and during race rituals. As someone else mentioned, water can do that. I don't drink before or during 5k's. I also have learned to recognize the feelings of impending problems and pull back before they arise. Experience and practice will take care of most everything so long as you don't give up.

Thanks for the support and advice everyone. I am going to give some of those fast interval type things a try. Can't hurt anymore, right?

just for those who asked, I've been running for about 3 years and average around 40 miles per week. I've tried eating, not eating, drinking, not drinking and all combinations of those before a 5k with the same result. I usually do a slow jog of about 1.5 to 2 miles for a warm up, but maybe I should pick that up a bit.

Thanks again for the advice.  I appreciate all that I learn here.

Just for the record, here is my preferred warm up keeping in mind that my 5K race pace is around 6:00.

1 mile very easy jog@ 8:30-9:00.

1/4 mile @ 8:00 + 1/4 mile @ 7:15 + 1/4 mile @ 6:30 + 1/4 mile @ 6:00 (easy effort, marathon effort, tempo effort, 5K effort)

Rest two minutes.

1/4 mile @ 5K pace + 1/4 mile slow jog (like 10:00 pace) + 1/4 mile @ 5K pace + 1/4 mile slow jog

Rest two minutes.

4 strides.

Hopefully, it all finishes 5-10 minutes before the gun.  In cooler weather, more like 5 minutes and in warmer weather closer to 10.  If temps will be above 75, I abbreviate the workout and skip the two 1/4 mile efforts @ 5K pace.  I just finish going up through the gears and then do some strides.

A bit of slow jogging is a great warm up for a marathon but it's not so good for a 5K.  You need to prime your body to be ready to crank it from the gun.  Without a fairly extensive warmup, you'll have a good chance of spiking your lactate levels and then you'll start to slow a good bit somewhere around Mile 2.  I agree that you need to do a bit of experimenting.  I did one warm up that lasted over 4 miles and found out that was too much.