Hi, Patakova, and welcome to the U.S. and to Psychcentral. To some small degree, I do understand what you're going through. I made a long move with my parents right after high school to a new place where I knew no one and had to find a job and start college. On top of this, I was, and still am, suffering from bipolar depression. I found a job pushing a broom in a ship yard. I felt like such a failure. I was supposedly so smart yet, with no work experience, no one would hire me. But, the big thing for me and for you is we are here with our parents and brothers. They can be tough with us but they can also be caring and supportive. They just need to understand what you're going through. Depression is a disease just like cancer or heart disease. We and they have to be educated about it.
About your girlfriend, it's really tough when that happens. My fiancé was cheating on me and it took her mother telling me for me to believe it. I thought I was going to die. But I got better and found love again. My wife and I have been together for 25 years. Wow, that's hard to believe she's put up with my crap for that long but she has. She's an angel for all I've put her through and staying with me. Either that or she's as demented as I am.
Plus, you're 20 years old! You're just a kid! Just take your time and get use to how things work in the U.S. and you'll be fine. Yeah, you're going to have to work some crappy jobs in the beginning but, if you can make a name for yourself as a hard worker, things will get better.
And, yeah, professional help is expensive especially if you don't have insurance but there's a group called NAMI that can help. They have local support groups all over the country and they're free. Just look them up on the computer. Plus, this site is free and it has a lot of great people who know what you're going through and they want to help.
If I can help you in any other way, feel free to private message me any time. Good luck and I hope you find the support you need to get through this difficult time.