This is Spot, she turned 13 last July. She's been overweight for her whole life. I was not the person feeding her until she was around 9, and since ive been struggling to get her weight down. Also around 9, I noticed some signs of arthritis. Last winter I began taking her to get a solensia shot once a month. It helped her arthritis so much, even though I could barely afford it. 

Last February when I started her on it, I had her down to 13.8lbs and the vet said I should have her on senior food instead of diet food. I listened, bought senior food, and in 2 months she was back over 15lbs. She eats less than a half cup per day. The vet gave me food guidelines, ⅜ a cup of kibble and a half 5.5oz can of wet food a day. I fed her the ⅜ cup plus ⅕ of a can per day (she will eat it too fast and puke if I give more) and she still wasnt losing weight. In June I went away and my roommates looked after her and she gained more weight, so now she would need 2 shots which I definitely cannot afford.

Ive had her on the triacta joint supplement for a month now and haven't noticed a change, if anything it seems to be getting worse (im guessing from the weather change). I really dont know what to do to help her. I want to improve her quality of life but I dont know how. Any suggestions on how I can ease her pain and mobility?

Suggestions on how to help my cat's arthritis?