For the past 2 months i've been having a lot of brown mucus discharge after p. that lasts for weeks. i don't have an infection. and im on birth control.

Breakthrough bleed: Breakthrough bleeding (bleeding at the wrong time) is very normal on birth control. Its no big deal and usually self corrects over time. If it continues to happen then consider using a different birth control method and scheduling a visit for an exam and testing. It's annoying but does not mean your birth control is not working.