For the past 4 days, I've had light spotting and mild cramping and I don't know why. I've also felt nauseated off and on. So naturally I think it might be implantation bleeding, since it started 10 days after I got a positive OPK. However, I just got a BFN today. I'm not expecting AF for at least 3 more days, but the box says it's more than 80% accurate at this time, so I'm guessing it will be an early AF. This has actually happened 4 other times in the past year (and never before that). Every time, I get my hopes up, only to get AF after 3 or 4 days of spotting. The doctor said it might be endometriosis but couldn't confirm without surgery. He ruled out PCOS. Could this be recurring chemical pregnancies? I've never actually had a BFP. Can anyone relate? Any ideas on what could be going on?