What Does The Brown Discharge After Unprotected Sex Indicate?

I had my first baby nine months ago, rough labor and what not, I hemmoraged real bad and had to have a dnc for my retained placenta, then a month after the dnc I got on depo birth control so I never experienced the postpartum period, I did the depo shot and have been off of it for 6 or so months, I have been having dark brown discharge light flow, the first time it started it was steady flow off and on for 7 days only a little bit, didn t fill much of a pad or anything, then after it stoped for week, it started again, steady flow like the fist time, it last for 5 days, stopped. Yes I have been having intercourse wit my partner, took pregnancy test both weeks I was experiencing the brown discharge they came up negative, but just three days ago I had some spotting, pink and brown very scary and light only viable when I wipe haven t had to wear a pad. Very different than the first two times I have had the brown discharge... this time it s only been going on for about two days, not a steady flow very random and very very light, no cramps nothing like the first two times I started having this brown discharge, no foul odor nothing. Just fatigue and been emotional a little bit. I don t know the fatigue has to do with working alot and having to be up at night with my baby. But I m tierd all the time. It might just be my body getting back on track from the child birth the dnc and the depo. I don t know if I have ovulated yet or if I havent, I haven t been tracking much, just my discharge that s all. Is it at all possible I could be pregnant? Or how long will it take for me to ovulate again? Is this normal from coming off the depo? Also I have experienced brown discharge like an hour or two after unprotected sex especially if my partner finishes without pulling out. Why is that?