Your upper arm problems may be due to arthritis in the upper spine.
Your thigh problems could be from arthritic hips or problems in the lumbar part of your spine (lower back).
Your profile says that you are 67 years of age, and it is highly likely that you have some form of degeneration in your bones. Your doctor would be able to refer you to have xrays or other imaging done to see what is going on with your spine and hip area.
The redness and itching on your thighs could be a fungal infection like Thrush. Your doctor can take a swab of the area to see if it is a fungal problem and prescribe you with the appropriate cream for this. Do not neglect this because it can spread and get worse. You may find bathing with a cupful of Epsom salts in your bath water and a little baby oil may help. Your doctor may prescribe an antifungal/antibacterial cream for you.
thank you for your replies. I do have fibromyalgia so that may be what it is. The rash, I'm not sure yet. I'm trying to rule out certain foods. Thanks again.
Possibly a neurologist or an internist would be the best places to start. Your symptoms sort of point to fibromyalgia, except for the rash, at any rate, a basic doctor visit is in order and they can refer you accordingly.
I would find a Nutritional Therapist in your area. They have special tests and techniques to help get to the bottom of your symptoms. It can be expensive, but worth it. In the mean-time, keep track of when you have your rash and what you have eaten. Sometimes when our health is compromised our body becomes very reactive due to inflammation.