Having been in a similar place around the same age, the things that helped me were: confiding in friends if you can, a therapist, finding the right medicine, and working on making things better one small, manageable step at a time.
Regarding medicine I know there are lots of stereotypes about what taking medicine to help with mental health issues is like, but I urge you not to write it off nor to give up if one medication doesn't work for you. It's a process, and one you need to work with a doctor with to find the right fit for you. Also, medicine won't magically fix everything on its own, it's just a little bit of help on the road to finding a complete solution.
Ultimately there are lots of good recommendations here. What works for you is going to be unique, and it's something you'll have the best luck with if you get some help.
Happy Fastmail user here. Has a lot of extra features.