Suggest Treatment For Tendinitis In The Elbow

I have been having health issues for a long time now. I was always very healthy. I Started to have pain in my knees and lower back a few years ago while training for a marathon. I ran the marathon and then stopped running (as recommended) to recover. It has been one thing after another every since. I have a lot of pain and tightness in my quads and hips. Some days are worse than others but not always due to over doing it. I just can t do as much walking or moving without having a lot of pain. I feel like my memory is not what it used to be and I just can t readily recall information like I used to. People say its just normal aging but it concerns me. I have had neuropathy in my feet and hands for the past 2.5 months. Some days are worse than others. Today I have a lot of pain in my right elbow. I was told I do have some tendinitis in this elbow but today its much worse for no reason. I m very frustrated. I know its not normal and something is wrong but I don t know what is wrong with me. I have had a lot of blood work. I have been told I have an autoimmune disease maybe.