Why Am I Not Getting My Period For 6 Years?

im 31 years old and i had my son 6 years ago. since then i have never got my period back and my stomach is badly bloated 24/7 like im 9 months pregnant. it hurts when i sit down becuase it pushes up on my chest, which causes me to have bad chest pains. i feel sluggish all the time and dont have any energy. i have been to the doctor but they look at me puzzled. i cant afford to keep running back with no answers, but im really scared. any help would be appreciated.