Have Irregular Periods. Having Weight Gain. No Medication Till Now. What To Do?

I have always had irregular periods..when I do get periods its usually after 2 or 3 months and it would stay on for a week..now I have my period after 3 months of no period and my period wont seem too go off its been on since march 15th up until now apr.5th..and the blood would change colors from brown too dark red then back too bright red again then it would start over again with the same colors in that pattern and the flow would be heavy then light heavy then light im starting too get worried because this never happened too me before..i am 22 131lbs and 5'5..im thinking its because my body change because I gained weight..someone please help me I would really appreciate it