Could you look in the mirror less? Seems when you look in the mirror you scrutinise what you look like, you think you look fat and this makes you feel bad. So.. perhaps NOT looking in the mirror in the first place could help those other things not happen? It has helped me a lot. I have a full length mirror in my room and have moved it so I can't see myself properly in it (I do keep moving it back out to check but that's not really my intention).
I think it might really help you. You know looking in the mirror will make you feel bad, and right now maybe there's not a way to look in the mirror and feel ok, so take away the mirror and you can take away the feeling bad, to an extent.

My therapist told me only look in the mirror to check your outfit looks ok. Don't let yourself stand there pointing out bits that look fat and finding reasons to feel bad about how you look.

I'm my goal weight now and I do feel fat when I look in the mirror, but I'm trying to change the image I see, trying to exercise so I look more toned and fit, it's slow but it is helping me gradually to accept what I look like, I feel like if I'm exercising I still have some control over what I look like.