I am on birth control for over a year but I don't always take them everyday or the same time, I've has brown discharge a week before my period and I am now two days late? What could this be?

It could be just two days late, few people are that regular, two days is really not even late.

So wait for about another week and if still no period do a pregnancy test.

IF you are not taking it regular, it is really of little valule.