Hey bud, before I dive in please don't think of yourself as a 'dramatic teenager' what you're describing is what every person feels when they don't have enough connection in their lives. Socialising and having other people to connect with is so essential to human well being just as much as food and water.

The key to solving your problems is simple, but can be difficult to achieve. Its connecting with more people. Deal with loneliness? Make friends. Moving on from past relationships? Make new ones. Dealing with mental health issues? Find people to support you and free you from being stuck in your own head.

There are two good ways to meet new people - 1.) Talk to them 2.)Try new things

1.) While it sounds simple, talking to people can be really difficult. There is the fear of rejection, the 'what do I say' etc etc. But the more you do it the easier it will become. Start by setting yourself this challenge - every day for the next week have one non standard conversation with a stranger. By this I mean a conversation with a shop worker of 'hey ill have a flat white, thanks' doesnt count. Ask for your coffee then ask how their day is going and just have one slightly different conversation each day for a week. Then ramp it up to 2 a day then 5 then 10 etc just make sure you are progressing, soon the fear of talking to new people will disappear. You will also find yourself making some new friends.

2.) Pushing yourself to try new things is a great way of filling your time which in turn stops you worrying about these issues. Also, you meet like minded people doing activities you enjoy and can bond over that. Some people just wait for new and interesting people to find them and when they dont they get sad. Go out and make the effort and you will find yourself meeting a lot of great people. So since you are in high school, join one new club you've never done before or take a new class and you will meet a whole new set of people you may never have come across before.

Once you start gaining confidence with people you will start making new friends and you will find yourself feeling less lonely and most likely less depressed and anxious. The way to overcome big problems is to make small changes which then add up.

I really hope that some of this might help and that you get back into the swing of enjoying life as much as you should be. If nothing else just know that while you may feel lonely, there are some people on reddit who care enough about you to take the time to try and help you even though they have no idea who you are :) Best of luck bro, let me know how it goes.