today i was doing crunches on a medicine ball which i have never done before and everything seemed to be going well until i was done my set and got up then felt a bubble sort of come up into my lower abs like a cramp or something and it hurt for about 10 seconds and i was fine? then i flexed my abs right after and it hurt again so then i streched out a little bit. i think it might be a pulled muscle in my abs. ever happen to anyone?