Confused. How's it possible?

Ok so. I had my AF this month the 4th-8th. Regular 5 days. Got a positive opk of the 16th and they were crazy positive for 4 days straight so I decided to take a pregnancy test cheapie right before I went to bed. It turned out to have a faint line. So I took a frer and it was crazy positive as well. Took a Clearblue advance digital with fmu and it said 2-3 weeks since ovulation (4-5 weeks pregnant). Well, 2 weeks ago was AF so no BDing then and 3 weeks ago I don't recal nor had I charted any BD that week either. How is this possible?