I had some really bad cramps as well on about Day 18 after stopping the pill. I thought I was ovulating but AF never came so it might be your body trying to get back to doing things but not quite getting there yet. I also got some really weird AF cramps midway through and nothing happened. I just kept track of everything that was going on, then when AF finally arrived, I could count back 14 days and see what the "normal" ovulation symptoms might have been.
I got my positive OPK today on CD17 of this cycle (my third since the pill), so it's starting to get back to normal finally now, so it will happen!