What to do about excessive bleeding during menstrual cycle? I soak through heavy and even overnight pads

See your physician. There are a number of things that need to be done. You need to make sure you aren't anemic. Thyroid testing might also be helpful. An ultrasound of your uterus can rule out benign fibroid tumors. If all of your testing comes back normal, oral contraceptive pills can be prescribed to decrease your heavy bleeding. Good luck!
Heavy menses. Persistant excessive menstrual bleeding requires medical attention. Call your doctor or gynecologist for an appointment for an evauluation.