Digital ovulation test says negative but i feel like im ovulating, why?

My cycles range from 31-42 days apart. I am on cd21 today. I've been taking digital ovulation tests (today is day 8 of using them) and I havent gotten a smiley face yet. I've BD'ed every other day since my period ended so I know I havent missed my chance this month. My stomach is hurting so much today. I get this way every month around ovulation. I'm just confused why my ovaries feel like they are going to pop from the pain but yet I havent gotten a positive on the OPK... Has this happened to you? I am still within the normal time frame for me to ovulate...and I'm even really bloated which is the norm for me.