You might want to see someone just to work through that now before you go down a painful road. Many people who tie their feelings of happiness and self-worth to their size find that they feel hollow and disappointed once they've lost a lot of weight. Even if you don't particularly tie the things together more than most people, it can still be hard to live with the new you in the old life because it's disconcerting, KWIM?

What about being that size makes you unhappy? If you lack mobility, you should work on that. When I was 290 and pregnant, I could still do a cartwheel. Not coincidentally, I never felt as bad at that weight as many people do because I had health and mobility. You can work on improving how you feel physically at any weight and you shouldn't wait on the scale to begin that process of taking care of yourself.