What Causes Weakness With Hot Flashes?

My Father is 86 years old, weighs 135 lbs. and is 5'9", and recently had catarac surgery on his left eye in March of this year. Since the surgery he has been experiencing hot flashes and weakness. He has been to emergency three times since and the doctors can't find anything wrong. He is on blood pressure medication and lipitor for cholestral, and one baby asprin daily. His family doctor prescribed muscle relaxors, but my father feels that this medication is too strong and puts him to sleep, so he does not want to take it. He recently went to a Chinese doctor and had one acupuncture treatment and was given herbs for his stomach as the Chinese doctor noted that he had a white tongue and explained this is a sympton of a bad stomach. My father does not want to take the medicine anymore as he feels it has the same effect as the muscle relaxors. He also has stiffness on the left side of his neck and it is difficult for him to move it without pain. Do you know what might be causing the weakness and hot flashes? He has always been a very active person and he is having difficulty relaxing.