Does anyone know what's wrong with me?

I'm 17. Although I do enjoy the company of others at times, I very much enjoy being alone. I have a few close friends and I love hanging out with them, but I try and avoid most other social gatherings. When my family come around to my house, I usually stay up in my room, hoping that they won't come up. I love them very much, but I just feel so awkward around them. (not my mum and dad, just my aunties, uncles, ect.) I only feel comfortable around them after I've drank quite abit. My auntie called me a "loner" a few days ago, and it really got me down and made me cry for some reason. I think it might be because I know it's true, and I hate it. I envy people who can feel comfortable around people and can talk to others endlessly. I just never know what to say, and this makes me feel really anxious. I am also very sensitive, and everything seems too much alot of the time. My mum is the only person in the world who I can trust, and I often think about how I'll hope when she dies. Morbid, I know, but I can't help it. Sometimes I worry that I might have some kind of mental disorder. :/