don't worry, weight gain is a well-known side effect of contraceptives (but I notice alot of brands now advertise no weight gain) .. I took contraceptives on and off for several years , one period of time I also had weight gain problem even though I exercise more and watch my diet I couldn't lose weight! (doctor told me it may be due to the pill), however other times I was back on the pill I didn't have this problem~~
I suggest you try to see a different O&G for another opinion about your bleeding problem ? get well soon! :)