Trouble getting positive OPK?

Katy • TTC #1!! Just married in September and focusing on stress reduction and healthy living habits
Does anyone else have problems getting a positive OPK even though you are very regular and are sure you ovulate? 
I have very regular 31 to 32 day cycles, ovulating on cd 18-19 with EWCM and positive OPK. The only way I can seem to get a positive is if I use room temp urine and at 2-2:30 in the afternoon. Otherwise, around ovulation I just get a close, but not quite positive. I figured I would O today, but only had a barely positive OPK yesterday and today with room temp urine. Yesterday evening and tonight's OPKs are definitely negative. 
​Does this happen to anyone else? Or do you think those barely positives count? I can't add a picture unfortunately.