Fake it till you make it and it may turn into your reality. You do not need to be in a relationship at 17 it’s not a must. Just because some other people your age are in a relationship it doesn’t mean you have to be in one. Wait until the right person cones your way and that could be when your in uni.
Friendships come and go and sometimes they are for the right reason. I went to a girls school so I have had some pretty big fallouts when I felt I was all alone but now I look back on it and laugh and I’m happy those friends are out of my life. Focus on the one friendship you still have, you are not completely alone.
Try to talk to new people as well, you do t have to be best friends with them but just people you know you can say hi and have a pleasant conversation with, and maybe later your friends may grow and blossom in future.
Being nerdy and political is not a bad thing, it just means you are smart and have a mind of your own, which triumphs over a lot of things and is what people love. Don’t hold it back, express it.
In terms of your family don’t always stay in your room, go down try to hang out with them a little more and talk to one person about how you are feeling fine to time. I hate telling people how I feel but talking actually makes it better and I know at the time you don’t want to believe it but it’s true.
Finally, going back to my first statement (fake it till you make it and it may become your reality), something that has helped me along the way is picture how you wish you could be e.g confident and outgoing, and try and do the things that make you seem and feel confident. Try to be a new you and be open to new experiences like maybe sitting with a group you don’t talk to so much at lunch and just talk about something random or join their conversation and make it seem like you aren’t scared or nervous but just felt like talking to people and they may see it as you are just outgoing. There are so many videos on YouTube that I like watching that lift my spirits when I feel down and teach me how to be confident in myself and with others.