Body image issues

My TD this morning brought up the belief that if I gain weight my husband will become uninterested and start looking elsewhere and eventually fall for someone else. (Shameful thoughts I didn’t even fully admit to previously!). I’m looking for help developing a new belief that works toward positive self image for ME- but can’t shake the need/desire to appear attractive to my husband (who is clear that he is attractedto fit/thin women). Current model: C: my body. T: if I gain weight, my husband will fall for someone else F: fear A: yo-yo dieting, constant scrutiny of my body, become shy in bed, avoid being naked/seen R: I want to be someone else 🙁