I feel for you brother. You're not alone. On top of what everyone else says...
You're going to feel better if you hit the gym and come home sore. Every little victory like that does a lot to help you out, and scientifically, exercising releases loads of hormones that make you feel less like a piece of shit. It may sound like a really insignificant sort of thing, just going to the gym once (or going for a run or whatever), but taking an action you don't want to take in order to better yourself will make you happy and it'll force you to value yourself. Army PT won't help like that because it's bullshit you have to do. Exercise on your own time is you investing in yourself, which really helps mentally.
I mean, I have days where... things are pretty fucking bleak, nothing matters, I have no motivation or energy, I feel beyond alone, and I want to just slip into a coma, but I realize that it's just some fucky chemicals in my brain, I get some sun, eat some healthy food, talk to some strangers, work out a bit, get outside, and watch a nature documentary or something, go for a drive, let the sadness happen, and after time I feel better for a decent while. You just have to power through that hopeless period. Maybe write down all the shit you're upset about and feeling on some paper and then burn it. That may sound like some gay hippie shit, but try it out. Seeing your inner problems burn can maybe kinda help in a weird way.
Also, it helps your self-image to help other people. Maybe volunteer at an animal shelter or do some real "nice-guy" shit. Even if your sole motivator is to simply not feel like garbage, you're still helping others so anybody would be dead wrong to criticize, especially yourself.
Drinking won't help. It's a temporary relief that'll make you feel twice as shitty later. Eating won't help for similar reasons.
Also, use work to your advantage. When I'm preoccupied with work and not getting deep into my head, I feel better.
Of course, also listen to everyone else. That's just how I tackle my inner problems.