Would start slowly, make one change. Once it becomes easy to stick with, then do another. Look for a support group in your area, using this is great, but being around others face to face help ... even if you are embarrassed, it will help in the end.
It hasn't been 13 yrs since I had my gastric by-pass, only 4 yrs, but I gained a good amount of weight back. But being around others going through this (face to face) is something I found to be helpful.
Good luck .... just keep trying, and don't give up.