Weakness, swelling, body achiness which travels

My fiance has done blood test to no avail. His right index finger has swollen up and he has a hard time bending it and it hurts. He couldn't lift his left arm for a day, but that clear up, but sometimes that comes back and he can lift it under shoulder height. What is so strange is that he has muscle pain intermittently from having it all over his body to isolating it to one leg or the other. When he lies down for a length of time the stiffness subsides and he can get up to walk around OK. He's 71 years old and has been very active all his life. He came down with type 2 Diabetes, but is definitely not overweight (there's no fat on him). He watches his diet and eats fruits and vegetables and lean meats and no junk food. He's complaining of being tired after doing a normal (for him) business day which does require a lot of walking around. This used to not faze him and he feels that something is happening in his body to keep him from his normal energetic self. He's really tired by early evening. All this just keeps reoccurring for many days now. Any ideas to what is going on is most appreciated. Thanks, Cheryl Tweet