spotting during my fertile window the day after sex:i’m scared of pregnancy

hi so i’m very terrified of being pregnant right now and i need a lot of help. so i had protected sex february 7th but we think the condom failed. i was scared of precum because he didn’t finish so i got a plan b but took it the 10th. i thought i was fine but then saturday february 15th we had sex again and it was protected for sure so there was no mistakes. later that night i started spotting a pinkish fluid which would change from pink to red to brown. cramps came with it. it lasted from late at night the 15th to the 19th. i’m so scared of being pregnant even though it was only precum i was scared of and i took a plan b. what could be making me spot? i’m terrified of implantation bleeding. my next period isn’t expected until march 2nd. i need as much help as i can get