Why am I like this? I'm so confused?

Hello. I am a 15 year old boy. I have always felt different to everyone, I avoid going out where possible, I fear asking people things in case I am rejected by them and I get anxious around people. After researching these I came across a few mental illnesses that could be applicable to me but (because I really don't want to go to a doctor about it) I just asumed that I had it but now my head feels dirty and unclean and I can't tell between what's real and what's not. So recently I tried desperately searching for a problem I could have that would explain everything so I could feel cleaner mentally, but that's just lead me to convincing myself I have problems. My (real) symptoms are: social isolation, anxiety, feeling of being worthless and unseless and no help to anybody, little or no distinction between reality and what's not real, being sad worthless and upset one time then another very energetic and ambitious, thoughts of hurting myself, feeling of wanting to destroy things and sort of "explode" during my energetic phases. Are these normal for my age or something more. My symptoms (both the real ones I've described and the ones I think are fake but are not sure) interfere with my daily life. Any additional details will be provided if needed