My Next Period Isn't For Another 2 Weeks But I'm

My next period isn't for another 2 weeks but I'm bleeding right now and have been for about 4 days and it's not light spotting it's heavier. I am sexually active but also on birth control and my periods are usually on time and regular and I've never spotted in between them before. I haven't had any period symptoms, I had some stomach and chest pain the other night but that's it. I dont know what it is.