I'm suppose to be on my period but is spotting, brown/dark red, i'm on the bc pill.what can this mean?

Nothing: Birthcontrol pills thin the lining in your uterus. This causes minimal (sometimes none) bleeding at the time of your periods (for most women a welcome thing). Period bleeding can be pink/bright red/brown or even black. No worries!

Many possibilities: Spotting or irregular bleeding is common in the first 3 months of any new pill. Missed pills also cause bleeding, so be sure you're not missing, but spotting/ bleeding can have other causes: pregnancy, fibroids, stds, a polyp. Bc other than pills may have spotting (the shot, implant, or progestin iud). See your dr to be sure.