OPK nightmare.

Okay, so, I got a positive opk on the 18th (glow predicted my O day to be the 19th) then on the 19th got a negative opk. Now the past 2 days ive gotten very positive OPKs. My cycles are irregular ranging from 29 to 51 days. We BD on the 18th and 19th and in between then and now and BD last night. I took a pregnancy test last night and it was negative (assuming I ovulated on the 18th).

Ive been cramping the past 2-3 days which has nevwr happened unless AF is coming but I dont have any other AF symptoms. I'm really achy, gassy and stopped cramping for the most part today.

What could this mean?