I missed my period in october. I started spotting in november for a month and three weeks, after that I had heavy bleeding which the blood was bright?

Birth control pills. There are a variety of birth-control methods which will regulate your menstrual cycle. Schedule a visit. This is a very easy problem to solve. Birth control pills, nuvaring. Mirena (levonorgestrel) iud and the Ortho Evra patch are all very effective.
Missed cycle. At age 19 if you are sexually active always consider pregnancy first especially if not on birth control. If on birth control pills, this could be a normal side effect of them. Other causes include not ovulating for a month or so. Abnormal thyroid might be an issue at your age as well. Go see your ob/gyn provider soon.