Why do I have so much pain?

Okay so I don't know how else to explain this. I blow it off because I feel like nothing is wrong. But something always hurts. Either my back legs or arms. It feels like my bones are on fire and and the pain ranges from REALLY bad to mild and when it's really bad it feels like my bones burning from the insides out and and like
My limbs are being ripped off. It's starting to affect work, like I'll wake up with bad pain some days and have to call into work. Ive had days where I stay home and try not to move, it's starting to make me depressed. Being in constant pain you don't want to do anything. At this point I'm extremely happy if I wake up with no pain. I'm missing out on my fucking life because of it. I've been to the doctors, had X-rays, MRIS. I'm fine.  I'll be in pain one day, schedule a doctors appointment for the next day and I'm not hurting the that day So the doctor will move my legs and arms around and ask me if it hurts and I say no because it doesn't. It started when I was 15 and I was told it was growing pains and now I'm 20, the pain is happening nearly everyday now. The more time goes on the more often I feel the pain. 
When I'm hurting,if I stop moving the pain stops. The pain is the worst in my legs especially in my thighs and lower back. It can sometimes radiate to my feet. 
I'm just so tired of being in pain. I'm 20 years old, I should feel amazing at this point in my life. I'm posting this in hopes of finding someone who has something similar and knows what it is. Doctors just kind of blow me off like I'm dramatic because I don't go in crying in pain.