please help, i’m so embarrassed!!

lately, I’ve been having brown discharge and I don’t know what’s going on? the last time my bf and I had sex, he pulled out and there was some brown discharge on my sheets from me and I’ve been experiencing it on a daily basis too.. It’s just really embarrassing to me and I’m not sure if it’s my nexplanon or what’s going on, please help if you have any idea what’s going on or if this is normal.