Navient Sallie Mae Fraudaly added a co-signer and charging me Double. This has been going on for ten years Rancho Cordova California

Ten years ago I attended school at M.T.I. I needed a co-signer, which I received. I persued my education with I.T.T., to obtain my Bachelor's degree. I should only have one private loan with Sallie Mae, but they say I have a total of four. My balances are not going down. I am disabled and unable to work, due to my condition. I have tried several times to get these loans discharged and the company(Navient, A.K.A.-Sallie Mae) are not working with me. They tell me I have credit cards and a car payment, which is a result of idenity theft. I don't inderstand, they are making monthly payments. I am having to investigate this issue as well. Back to the private loans, I feel that they have overcharged me and not working with me and putting me into a spiral downfall with these loans. I am on the brink of a mental break down. Please help me!