14-15 is the worst, most cringe, socially awkward, depressed time of a young man's life, barring unfortunate circumstances at other ages. (For example if you had a crippling injury at ag 19, I'm sure that'd be worse).
Once you grow out of this pubescent phase it will be so much better. gf at 15 doesn't even matter either.
a gf in high school would indeed be nice, though. But 15 is pretty young so it's no big deal.
Some advice I would give to myself at 15 (and I wouldn't have taken it anyway, I guess):
1. GET A PART TIME JOB. This may be one of the single best things you can do for yourself. Having even a small amount of disposable income makes a world of difference. When you're a student and you go from having zero dollars to even just a hundred a week the difference is crazy. You can go out with your friends to restaurants every single day after school. You can get yourself games (but you should stop playing games anyway). You can get clothes, snacks, little things you've wanted, whatever. But the biggest value of it will definitely be using it to go places with people, and putting it to use building hobbies. I'm assuming you at least have friends to go out with to places. Having a social life is a very important thing. Also I noticed that when you socialize more often there's a higher chance of meeting girls.
Another reason to get a job is not just to spend the money but save it. Spend some of it on things that make you happy, and save a bit of it. By the end of high school you may have a decent amount saved.
And when you work you have to interact with people and it helps you get better at it.
2. GET OFF THE COMPUTER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I can't stress this enough. the computer destroys your ability to focus or appreciate some aspects of life. it makes you a recluse, sedentary, and weak. Use the internet as little as possible. You NEED to figure out some alternatives here. Start reading short books and as you read you'll notice your attention span coming back slowly, and then you can keep reading. Reading a good book is a lot better than scrolling online. And imageboards are pretty bad too. If you just stuck to this one in particular then I suppose it's not too bad at all. But watch out.
When I was 14-15 I used to go on /r9k/ on 4chan. I had some good times but overall it was a depressing waste of time.
Figure out some things you can do that's not at the computer. Write your ideas down and use a sheet of paper. Here's where having money helps because sitting at home is free and sometimes you need a bit of money to go out and do stuff.
A list of alternative activities to being at the computer can look like anything. maybe it looks like this:
-read a novel for entertainment
-read a nonfiction book
-learn some skill of your choosing (insert whatever here) like how to ride a wheelie on your bike.
-go for a walk/jog/hike/bike ride
-draw or try painting something
-go out to the park and meet some friends, play a sport or just talk
-go to a restaurant with your friends