It's hard to determine when you need to stop thinking you might be pregnant when one is not sure of ovulation/appx. ovulation. But if I had to guess, I would be inclined to think that by this point I wasn't pregnant.
I tried for 2 1/2 yrs to conceive and in the meantime I got familiar with my overall fertility. I don't ovulate regularly nor do I ovulate on the same day every month, so I learned to track my ovulation through BBT Temping. Research a little on it, and use Fertility Friend to track it. You will never again have to wonder if you're late or not. Also, once you become familiar with this method, use OPK's to help track ovulation. In fact, opk's are what helped me recognize I was ovulating and timed intercourse accordingly, and now I'm expecting! I truly wish you the best!!