Unfortunately no one can really give you the answer or mainly the solution to your problem. It seems you're a giving person which is great, I believe I am too and see people take advantage of that sometimes. If that happens I try to realize that not everyone's like me and a lot of people simply don't stop to think about others. Some people give everything they can to help other people, not because they expect something in return, but simply to make someone's day in some way. A lot of people seem to not notice it for what it is though, and when that happens I think it's just best to not think into it too much and simply move on. It's something that can be extremely hard to do.
It's easy to just sit around and say "how dare she walk on me like that, all I've done is be kind to her!", but it's hard to convince yourself to not care or at least not get down about it. Especially when it constantly happens. Which I promise you, it will. But that's how people are and you've got to find a way to deal with those things yourself.
Not going to lie, I'm actually trying to find the solution to a similar problem for myself but it's not simple.
And about the depression again, no one can solve that but you. It sucks, truly does. But there's no miracle advice anyone can give you. All you need to do is find a strong motivation for yourself. Not for another person, but for yourself for once, because you can't rely on other people for your own happiness, which is something I've recently learned. If you rely on other people for happiness, you're just going to get shut right down. The only person who's reliable and responsible for your happiness is you.
Getting over things like this seems like such an incredibly hard thing when you're in a rut, but it's something every person has to learn to do because there truly are many good reasons for any individual's motivation and happiness, you just need to consciously find one and dedicate yourself, to yourself.
Either way though I do hope you can find something that works for you, man. And just a tip, the drinking thing won't help. If you're anything like me drinking may seem like a mood lift, but it's not. The only reason it seems like it is is because your thought process is slow and distorted and you probably don't realize how sad it may actually be making you. Though everyone's different so it may not be the case for you but what I can say for sure is that drinking is a temporary solution by all means. Not to mention usually people just feel worse about themselves afterwards. I'm sure I don't have to tell you though because I'm sure you've heard it a million times but man, it's just not a good idea.