I can totally understand what you mean.

I am in recovery from a 15 year long ED and am very careful protecting my recovery. I was given SSRIs a few years ago and was terrified about gaining weight.
I spoke to my T about it for a long time before I accepted that I really did need the SSRIs and began to taken them.

They actually didn't make me gain weight. If anything, I lost a small amount (not much) which was due to the nausea I experienced for the first 6 weeks or so.

I know its obvious to say, but you really need to discuss this with your T.