You can get pain from ovulation, too, I think. I've had it happen several times; it'll be so bad it hurts to sit upright, let alone stand, and nothing that treats GI stuff will help it, while pain killers will. I usually just wind up going fetal if I'm home, or trying to ride around on the bus for awhile so the vibrations loosen me up if I'm at school (we have free busses running around all the time).