Well, I m a 17 year old girl. I had sex for the first time in December, I was 16 then. My partner and I used condoms until I started depo provera birth control . I ve been on this birth control for about 5 months, and I ve had two shots. I haven t gotten a regular period in that time, but there was occasional spotting. Lately, after sex I ve been bleeding lightly, and sometimes afterwards I m sort of uncomfortable down low. Please tell me what is the most likely reason for the bleeding.