Help please

I’ve been taking ovulations for almost a year now. I started last September. Well. I never got a positive until I was pregnant in January. (Had a miscarriage) after that I’ve been able to see I’ve had one actual positive ovulation test every month. It hasn’t been different. Last time I was pregnant I had positive opk tests for about two weeks. I never got a dark line on a pregnancy test though but a miscarriage was confirmed with my doctor. I have O- blood too so I’m not sure if that will effect anything. This month I’ve had positive opk tests since 6/03/2019. I’ve tried taking different tests too but I’m just not sure. Both sides color matches. They’re as dark as each other. Has this happened to anyone else?