Suggest Treatment For Prolonged Menstrual Bleeding

I got my period a week early and I've been on the pill for 7 years and never once has this happened. I did skip a pill but I've done that in the past by accident and nothing happened. I've now been bleeding for 8 days (longer then usual) and I am now on the placebo pill. Today would be the start of my period any other month. I've been very regular. I would like to know if I should be patient and wait to start the active pill before freaking out, or if I should see a doctor right away. I have an appointment with my gyeno on April 30th which isn't too far away. Also, the blood is very dark...like a brown or black colour. What could this be from? I've also lost 25lbs in the last year, I'm 25 years old and I'm sexually active. Please help!