I relate to what you're going on and want to send you my love and support and tell you that it is completely understandable.
A book that may be of interest to you is: "Fat is a feminist Issue" by Susie Orbach... It's not in print in the US anymore, but you can buy a used copy on amazon. It is, however, in print in the UK and you can buy a new copy on the UK version of amazon.
The first half talks about what people have invested in gaining weight, especially if they were not always overweight, and one of the things she talks about is essentially gaining a layer of insulation against men. I really found it incredibly interesting. I also gained about 70 lbs extremely fast, and was never overweight before in my life. There are several reasons my body/min may be invested in being fat... though I'm not really emotionally up to going into them here. The second half is about starting a support group, and honestly I never read it. If you have a therapist it sounds like you're doing the right thing!
Don't be put off by the 'feminist' title if you'd be prone to that. I'm not, but I just thought I'd throw it in there...