Opk’s

Can anyone please tell me why I’ve never had a positive opk? I’m 34 have child age 6 (previous) my partner is 26. Came off pill March 2016. Pregnant sept 2016. MC December 2016. TTC ever since. My bloods say I’m ovulating... or could that just be the hormone peak? And possibly I’m not releasing eggs? My cycles are pretty regular ...