I'm tired of bleeding....

I've been on my period for a week and a few days now, when usually it's only like 4-5 days. I'm on birth control but I've been on it for maybe 5-6 months. My blood is also quite a bit darker than it usually would be for my period. Some days I'll bleed like it's the first day, then the next I'll barley bleed the whole day. Any advise or anyone know what may be happening? 🙃