Weight gain post surgery

I have gained at least 15 pounds since total thyroidectomy March 10. I had RAI in June. My last TSH was 39. My levo dose is 150. My next blood work is in September so I hope my TSH has come down. I am frustrated because I do Weight Watchers but nothing seems to work. I am 78 but very healthy and active. Is there hope I can figure this out. I also have muscle fatigue but really no other symptoms.