please help!!

i have been on birth control for over a year now and i take it perfectly. Last month i had unprotected sex and i’m pretty sure some of his cum got in me. For that month, my period was super light- like barely there, it only lasted one day and that never happens. I took a pregnancy test after my “period” and it came back negative, at that point it had been 2 weeks since i had sex. Now, i’m in the second week of my new pill pack and i’m spotting, but it turned into almost a light period with cramps and more bleeding then on monday when it started (it’s now wed). Even though i had a negative test my ocd self is still freaking out and need some reassurance/ insight on what is going on with me. Please help!