Had unprotected sex 2 weeks before period was due
When my period was suppose to come it was brown stuff for like 2 days I am on BC but I wasn't taking it reguraly
And I eventually just stop taking it about a week before I was suppose to get my period.

If your period is unusual and you could possibly be pregnant I would certainly do a pregnancy test, especially being on birth control, which can be dangerous to continue if you are pregnant.

It could also be caused by other things such as an infection so if you aren't pregnant, go for a check up.

Thank you