I Am A 56 Year Old Woman And Am Having

I am a 56 year old woman and am having issues with severe muscle loss. Yes, I have been going through menopause for about 11 years and I'm sure it may attribute to some of the loss. It's hard to explain, but I'll try. Ok, I don't seem to be losing weight, in fact over the past 10 years I've gained a little. However, my cloths sizing is getting smaller because my muscles seem to keep deteriorating and I can't figure out why? I've asked my doctor and she just kind of gives me a blank look. She is now sending me to a physiatrist which seems weird to me (aren't they back pain specialists?) I would like to find out if there could be another issue going on but who to turn to??