I have a lot on my mind today.

So basically I've just got a lot on my mind and I just need to work it all out.
I'm feeling really anxious today. I don't have anxiety, but I'm feeling anxious.
All day I felt that people were judging me. For example I heard people laughing and instantly though they were laughing at me even though it was probably nothing to do with me.
I just started at college and already I've kind of been labelled as a nerd. To me that's a good thing. I'm proud that I work hard and take pride in my work. But sometimes others don't see it like that.
I just feel like I don't fit in. Like I drift from place to place. In my lessons I kind of have a few friends in each but it's not exactly a close friendship, just someone to chat with in class.
So I'm kind of lonely.
I had a really close relationship with my friends in school and I'm not in any classes with them for college so I really miss them and it's like they're slipping away from me.
I recently found out that one of my friends cheated on her (now ex) boyfriend by starting to go out with someone else without breaking up with him, and it's tearing me in half. I care about her so much but it hurts me to think that she would do that.
I've been thinking I have depression for a while. I've not been diagnosed, but judging by my mood, it fits. There's a mild type called low mood which I think fits me.
I'm questioning (well tbh I'm kind of over it and not labelling it at the Mo) my sexuality. If I have to label it, I go under bisexual but I don't really care and I'm not comfortable labelling it openly at the moment.
My girlfriend of 9 months (I'm a girl) is kind of pressuring me to tell my parents about us. They know of us as just being friends. Like I said, I've not labelled myself, I'm not happy to put myself if a box, and even if I was my attitude is that my sexuality is my business and nobody else's (apart from maybe who I'm dating) and therefore nothing to do with my parents. This isn't a major issue, she's not massively pressuring me, but she's started to get a bit funny and awkward that I haven't told them. I don't think they'd react badly, I think in general they're supportive of the lgbtq+ community, but applying it to their own child might be different. And again, I don't see it as their business.
I'm also feeling quite stressed because college is quite intense. I'm worried about keeping up with the workload, and I'm really worried about having time to revise and how I will cope with exams. I only just got through my GCSEs.
The future also terrifies me. University seems like such a way off, but this time next year I will have to have applied. That's really proper scary to me. I still don't completely know what I want to do. And I don't feel ready to grow up.
My older brother is autistic, and I'm worried about his future. He's not going to university because it's just not his style and he wouldn't cope, But so far he's made no effort towards getting an apprenticeship, or a job, and I'm worried he'll just do nothing with his life.

I'm also worried about the state of the world. Politics gives me a headache, and I'm seriously starting to worry that we're heading towards world war three and I'm worried for the state of the world.