should I stop running (Read 163 times)

I took a 2 week break and then started running again.  During my runs, I have found that my left calf area has this weird feeling (like a tight, kind of fatigue feeling).  I'm not sure what it is, but stretching doesn't help.  It does make it hard to run, though, and slows my pace.  

What should I do?  Is it serious and if not, can it become serious (should I stop)?

Also, how long does it take to get back into the shape you were pre-resting period? (like, able to run same distance at the same pace.  ie: before I took a break, around 7minute pace for 6-9 miles was pretty easy, but now the pace is around 8)