I have been getting large painful cysts for years now. in the middle of my chest, groin are and now in my mouth. why is this happening?!

Unsure: You really need to be checked. If it were just your skin i would be less concerned. With your mouth also, get checked.

Painful cysts: You should see your MD ASAP for a diagnosis as this is not a dental issue.

May Not Be Related: Some people are more susceptible to cysts. If the cysts are in the exact same spot, then a doctor can remove the sack and prevent the cyst from recurring. Since you have cysts from several areas, you should see a dermatologist to help determine the cause and an appropriate treatment.

Check with your MD: in order to get a proper diagnosis. Some tests including blood test and biopsy will help your doctor to properly assess your condition.