Gaining Weight after Surgery?

I had some gall stones 10 months ago, and had my gall bladder removed. I have been steadily gaining weight since then. My doctor and surgeon never told me I would need to change my lifestyle afterwards.. And my nutritional science teacher said that I did. I weighed 180 when I got the surgery and now I weigh 212. (I just weighed myself) I Should weigh 115-125. I am 5'5" and female, and 20 years old. Am I gaining weight because of the surgery, because of no gall bladder? I also always feel tired, light headed, (I feel the urge to sleep 12+ hours) I can barely get up in the morning, I have trouble being active. I have severe asthma, and exercise is hard to do. Right now I feel very light headed. I have weak joints and have dislocated my knee 3 times. I wish more than anything to get healthy and lose weight, but I have had trouble with money. SO I can't afford healthy food... And I have no will power.. I also am on Birth Control. Implanon,