It’s hard to know from your letter if you are having symptoms of a psychological problem or if you are going through the usual, though painful, growing pains of being 15. There’s no getting around the fact that adolescence is a challenging time of life for just about everyone.
I can tell you think hard about things so perhaps you can consider some ideas.
It’s not at all unusual for kids your age to try on different activities and interests and reject most of them. It’s like trying on jeans. You might take 20 pair into the dressing room and only buy the one that fits best. You don’t scold yourself for not buying the other 19. They just didn’t fit. The same thing applies to trying on sports, hobbies, and interests – even people. It’s also not unusual to feel uncomfortable socially or to not have a girlfriend yet. It’s a little appreciated fact that over half of young people don’t have a special boy- or girlfriend while in high school. These people need to get into a new environment with new people to meet the right person. And it’s also not that unusual for a young man your age to feel angry and irritable. Your hormones are changing. You’re aware of more things that you find troublesome. You don’t like being treated like a kid anymore.
My advice is that you be patient with yourself and take more charge of your life. If you want better grades, a young man as thoughtful as you are can decide to do the work to get them. If you want to socialize more, put yourself into situations where you get some practice (like an organized club or theatre group or sport). You are doing well controlling your anger but you aren’t figuring out what you can do so that you aren’t in situations where you might get so angry. Maybe, for example, you and your folks are at the point where you can discuss your differences differently.
On the other hand, if you start to have trouble with sleep or appetite and find that you are irritable more times than not, it’s possible that you are getting depressed. If you think that might be the case, ask your folks to make you an appointment with a mental health professional for an evaluation. Having a counselor to talk to can prevent a depression from getting worse and can help you learn skills to get back to your usual self.
I wish you well.