People here will try to help but honestly while they may be well meaning (like me) and genuinely offer good advic, you really need to speak to someone.
You said you went to a GP a few years ago. That's a huge hurdle you've overcome already, a lot of people find asking for help to be the most difficult part. But you've done it and had the rotten luck to not have a great GP at the time. You've got strength that others don't. Does your college have a counselor or chaplin you could speak with? If that route might not be what you're looking fo, someone here recommended aware.ie sometimes speaking to a complete stranger, who's only job is to try to help, clears your head.
In most cases they will have dealt with young people having difficulties like your own and can point you in the right direction, you're not alone, not the first or last to go through this. You're not a drama queen or attention seeker, you're asking for advice and help, you should be proud to have the courage to do that. Many suffer in silence alone.
It's tough if youve no one to support you. But talking will and does help. A burden shared is a burden halved. There are no quick fixes my friend. One day at a time, hour by hour. You'll get there.
People can be well meaning but often sick their foot in it and think they're helping. "Just snap out of it" is probably the worst I've heard.
In the meantime if you feel really bad, go outside for a walk. Find some greenery, pet a dog, if you can get to the zoo or park, I found watching the animals helped me.
The booze can become habitual. Break that cycle, get out of the house on weekends, create new habits. You might have to really, really, really force yourself and use all your strength to do this, but it will help.
Stay strong, you're not alone. Everyone's been there or will be there.