I would suggest researching Insulin Resistance, that (i think if I read correclty) is why you have troubles loosing weight... I cant imagine its going to drop off to a point where you get stretch marks, but these days you can buy special creams to avoid that happening... check with your pharmacy and look up ways to treat insulin resistance?
Good luck
I was diagnosed at age 23 when my estrogen and testosterone levels tested way too high, so my doctor put me on birth control to fix my hormone levels. Is your dilemma that you can't lose weight? Have you ever gotten your thyroid levels checked? Look up the symptoms of hypothyroidism and see if you think you are experiencing them - trouble losing weight and irregular periods are two of the many symptoms.