... recently started taking a 50 mg dosage because my thyroid is getting worse..but about 2 weeks ago i was bleeding dark brown blood..and then today me and my boyfriend had sex and i went to the bathroom after and i was bleeding..it wasn't brown but normally red blood. i have never bleed during sex..not even when i lost my virginity 3, almost 4 years ago. i don't know if i'm pregnant or not, i should start my period in another week..but i'm taking birth control..if i am pregnant can me taking birth control hurt my baby?