20 Day Period

I'm really concerned about my period, I had a normal period on march 8th-13th then a little over a week went by and I started another period. It's still going! I'm cold, tired and weak all the time now, I can barely even get my work done but the school is almost over and I'm a senior! I've been trying to just bare through it but it's really hard. I don't know what to do.