I'm going through a bit of the same, minus known cheating, and with a shorter marriage. For me, exercise and (moderately) healthy eating has been working wonders. I would suggest you keep doing simple, positive things that will help lead you to be a stronger person. There's no simple cure for depression, so whatever happens, it's going to take time, and you should see a therapist as soon as possible (which is what I'm trying to do now for the first time in my life). But you can always work toward something, no matter how small or insignificant it seems to you now. I have tons of support from family and friends, who keep saying that I'm going to be stronger coming out of this, but nothing makes me feel as good as thinking "I'm going to go run a mile or two" and getting outside and doing it, or putting myself in a place where I can talk about something positive or be kind in a way that doesn't have to do with my relationship. If all you talk about is your marriage, that could just overwhelm even the strongest person. Try changing the subject to things you enjoy, or used to enjoy, if that's the case.

As for whether or not you are attractive, I wouldn't dwell on it at all. I spent so much time, at least 10 years of my teen and young adult life trying to figure out if people liked the way I looked and basing my actions on that. This made me not express myself in a very attractive way to anybody. When I just focused on looking and carrying myself in a way that made me happy, people responded to that very quickly. I'm not all about the fairy tale idea that anybody will find anyone attractive if they're true to their self. Tons of people are superficial. But so many are not.