I have a 100m and a 200m tomorrow.........

and the problem is that yesterday, it was my friend's birthday party and that I swam for like 3 hours.... Moreover I was swimming really hard (racing) so my whole body aches.. but the real problem is that my abs are really killing me. Even if i cough it hurts.

So are there any ways to stretch it out somehow? Any good websites that tell you how to stretch that part??

I have a really big race (100m - two times / 200m once) and I am aiming for 1st place so I really need to do good...

Also I have practice for tomorrow's race. Should I go even if my abs hurt? I'll make sure I dont over practice...so if I practice a little would it be better for my abs?

I really need urgent help since I cannot get help from a trainer or anything right now.