What's wrong with me?

I don't know what's wrong with me. This is starting to bug me alot. I feel like I'm slowly going even more insane. I keep trying to help myself and I get worse. I try to ignore it and I get worse. I really don't know what to do.
I'm always in physical pain cuz of my arthritis in my knees. I get leg spasms and cramps randomly throughout the day. I get headaches alot when I'm in alot of pain. I'm always depressed and friends have left me alone and now I feel alone all the time. Recently a few people I've been close to for a while have left me too for no reason. I'm not rude or mean to anyone, but for some reason people just leave and don't wanna talk to me anymore and never give an explanation why. 
I can't sleep that well and have been having nightmares again. I really wish I could forget them, but I can't. My boyfriend has been there for me and has always been there for me, even when we weren't in this kind of relationship. He's always been there and I'm afraid of him going away too. He's always been a great friend to me, but I'm still hurting alot from the pain I constantly have in my head and in my body.
I'm way too emotional in the first place and wish I could at least control it more than I do. I've tried different techniques and nothing works for me. I feel like I'll always be like this. I feel like I'll always be alone, depressed, in pain, and have no one. My boyfriend said he'd stay with me no matter what happens. But, other people have said that too. I really really wish I could believe him, but it'll take a while before I do.
I'm mainly just tired of everything now. I'm tired of all the pain I have to go through. I silently hear my brain screaming for it to stop and can't help myself to relieve it. The pain is so strong sometimes I just get very fatigued and fall asleep for a long time or take alot of naps. I feel like I'm slowly dying everyday and I can feel every second of it. It just hurts to exist and I wish the pain would just stop.
I always slowly rock myself back and fourth with tears in my eyes just about every night because the pain is so strong. I just try to go to sleep and half the time the pain keeps me awake. I don't like sleeping during the day because if I do then I'll be up more during the night and I hurt more at night.
The only time I'm not in pain is when I'm sleep. But, I barely even remember that and wake up alot because of leg spasms, leg cramps, nightmares, or having bad anxiety.
Nothing really gives me hope anymore. When I was younger I said that I would find out what's wrong with me and fix it myself. But, I don't know if I can keep doing that.