I have knots all over my body. On my back are faty tumors was told from doctor but I don't know bout my arms?

Get information. You could have a condition called neurofibromatosis in which benign tumors arise from peripheral branches of the nerve supply. This is inherited (do other members of your family or ancestry have this?). See your internist or perhaps a dermatologist for more information.
Tumors. Maybe lypomas , mobile non-tender rubbery irregular...Benign. Maybe genetic, can be neurofibromatosis (benign, bur disfiguring). Any mass which is growing, changing , becoming tender....Get it checked.