I get bloating and cramps, but right around ovulation. In fact I usually bloat more than I do with my period. I gain about 3 -5 lbs and get pretty bad cramps. For me that's about a day after the OPK is positive. I am not sure if it comes just before or just after, but must be close to the day given all the other indicators. So definitely can happen! Is it possible you are ovulating later than you think? Have you tried continuing to use OPKs after the first positive? How does your period align relative to the OPK and bloating/cramping?