There are several conditions that can cause such heavy bleeding. Adenomyosis can cause heavy non-stop periods with heavy clots, as can fibroids and polyps. A hormonal imbalance (thyroid or ovarian) can also create strange cycles (though they usually stop) - being overweight can extend periods because fat creates estrogen. There are also some bleeding disorders like von willebrand's disease that can manifest themselves with neverending periods.
Extended bleeding is a horrible drain on your energy and your circulatory system. Find a new gynecologist. There are lots of very simple procedures and hormone therapies or drugs that can help you. If you're overweight without a general cause (inactivity and eating too much) can indicate much more serious conditions, including thyroid or pancreatic imbalances.
Don't let it go on untreated - my sister ended up with an emergency hysterectomy at 34 - she was bleeding to death from adenomyosis. She's doing fine now, but i'm sure she would have liked a few more options if given the chance.
Take care.