Brown discharge before period?!

I’m 20 and have been on birth control since early high school and rarely miss pills. My period is supposed to be here in two days (I’m very regular because of the pill) and I started to have brown discharge two days ago with some cramping. I have never had “spotting” or brown discharge before a period before, but I always have cramps before.

This month I took my first pill a few hours late, so maybe that’s affecting it? Just hoping someone could calm my nerves. I know it’s normal for women to have brown discharge before their periods but I’ve never had it before so I’m worried it’s implantation bleeding.