I know some people use OPK's as pg tests, but I wouldn't call them more reliable than a HPT. They aren't designed for that. I would say that you are ovulating late - don't forget that you only came off BC at the end of last month - which was just over 2wks ago. It is highly likely that your body is readjusting to not having chemically manipulated cycles and your 'real' cycle may be a bit longer. In theory, you still have 9-10 days left of your cycle - so it is highly unlikely you are pg and you are actually detecting ovulation. It's not impossible you are pg, but just very unlikely.