Clomid & Ovulation Cramps

Maddie
So I've experienced what I am assuming are ovulation cramping both rounds I've been on Clomid. First month I had a positive opk I had cramping that evening. This current round I've had cramping last night & today - got a positive opk this afternoon (CD18). 
I know a positive opk usually means you'll be ovulating within 12-48 hours or so. 
Does any one know if the ovulation cramping happens as ovulation is occuring ... or prior to ovulating? 
Thanks!