Nobody is perfect, everyone has faults in one way or the other. The trick for a happy life is to continue to work on your goals while accepting yourself and your current situation. Living with a partner that is constantly reminding you that there are other people in their life that are in some way, even if it's just in the looks department, better than you, can be really weird.
Sometimes people that were skinny or fat in the past but somehow managed to fix their looks, by dieting, exercising or surgery, tend to over-focus on the way that they looked in the past. So now even if they are not fat or skinny anymore they are overly critical not only about how they look but also about how other people look. This over criticism combined with negative pessimistic outlook coming from the past experience can be a confidence killer for your partner, and you should stay away from it as best as you can.