When did i ovulate

I got a postive OPK the 14 of March. I wasnt taking temps right before that so was just going off opk's and not temps. But i kept taking temps and missed my period completly. Ive taken test which are all negative and have had cramps. Like the same spot throughout the day the past couple days. I took a FRER this evening and got a faint but wondering when i ovulated.... If i ovulated when i thought i did the line should be darker by now?