What Does It Mean When I Get Really Hot Inside

What does it mean when i get really hot inside and my feet sometime is hot and cold. I swear in my head and neck area. It comes and goes. I am getting weaker and weaker. I cannot do anything without and quickly getting tired. I can't stand for long. Had a heart scan done and it came back fine. Blood test was fin except I am a diabetic so numbers were in the high risk area. I'm taking metaformin for this. Estrogen level were low, but went to the gynecologist and said the low levels are normal for older women in the 60s. We think it is hot flashes but it does not explain the tired feeling. Total lack of energy. The 2 doctors I seen said it my be a virus and I was given a prescription to treat virus but that didn't help. Please advise.