Cramping with No AF & a Neg OPK

Em
Hi ladies! 
My husband and I have been TTC #1 for 4 months. I have a hard time tracking ovulation so I started using opk to help. I haven't got a + yet but had some cramping on my lower right side. Is it possible I'm ovulating and the opk didn't catch it? I alway test under the same conditions and time.