Why do i always feel down?

I always feel really down, like I have no hope or faith in anything. I barely eat and when I do I often feel disgusted by it and I don't eat it all. I take hours to settle enough to sleep then have nightmares and wake up late. I don't want to leave my bed or my house most days, I feel like it's pointless because I have nobody. I don't trust anyone and I'm paranoid. I think my relationship is about to end and I self harm. I lash out and I'm mean when I don't mean to be. I'm gay, gender confused and pretty much confused about everything. I don't know what's going on and I just want to feel okay. What could be going on and what can I do?