I've been bleeding heavy and having big clots for a month. I'm still very weak and still bleeding and clotting a lot. Do I need a blood transfusion?

Get checked. A simple blood test will tell you if you are anemic and how severe it is (a CBC or "blood count" to measure your hemoglobin). Women with ongoing bleeding should take supplemental iron to help regenerate blood. It's not likely to require a transfusion from heavy periods and ongoing bleeding. More important is getting checked to find out why you are bleeding so heavily. Please see a gynecologist.
See a doctor. Please have your parent(s) bring you to see a physician.