please someone tell me I'm paranoid

Okay so I had sex about 13 days ago I had twice in a row within 24hrs with different guys not my intention one which I don't remember and didn't press charges because i feel like it was my faul for happening which my bf knows about and well I took a plan b 3days later and it all happened when I was ovulating like the most day that I likely had a chance and today a week before my period I thought I had gotten it but it was just one spot the whole day passed by and I was like okay whatever it was probably not even blood but then again I went and I examined it and there it was again and I'm scared it might be implantation bleeding but please tell me it's not possible I took the plan b as fast as I could but it's not an easy buy like i really don't want to be pregnant especially of a sex I don't remember having with my friends ex bf my bf is aware of this since I haven't been able to have sex with him since then