OPK's , Clomid & hcg injectable

Massy • Mommy of preemie twins born at 29 weeks with IVF fresh transfer
Hello ladies, just wondering if anyone tested with OPK's after Clomid and hcg injectables??????
I'm on cycle day 15 and no positive opk yet :( I did feel cramping on cd 13! What could it have meant????
So confused