Is it normal for a sexually active 14-year-old who uses birth control to regulate her periods to get a brown discharge?

It really depends when you are getting this brown discharge. Brown blood at the beginning of a period is quite normal. Brown blood for a day or so at any other time during your cycle is not normal. If you are meaning that you are getting a brown discharge everyday throughout your whole cycle, it sounds like the pill that you are taking is not strong enough for you. It is not strong enough to regulate when your body is to bleed and when not to bleed, meaning that you are bleeding a tiny bit everyday. I would go back to your doctor and get a different prescription for another pill. There are many to take and you need to find the right one for you. It is NOT normal for a 14 year old to be sexually active, in fact it is ILLEGAL.