implantation bleeding v spotting?

im on cycle day 24 and i have three more birth control pills to finish before i start the placebo pills. im on the tri-pill (not mini).

this is the second month of being on birth control!

i have had sex four times *all with condom*

first time being on july 17th (22 days ago)

today i noticed there was brown discharge. thoughts as to what this is??