For The Past 2-3 Months I Have Had Low Energy.

For the past 2-3 months I have had low energy. My weight has been stable but I have lost muscle tone and gained fat as none of my clothes are fitting. I've been experiencing hair loss, and aching in my back between my shoulder blades. For the past month I've had severe constipation and now as of the past couple of weeks I get frequent episodes of my face and ears feeling very hot and pressure in my head. There is no visible flushing. I think I am also having hot flashes as I get periods of feeling hot and sweating although the temp is mild to cold. What could be causing all of this? I'm tired of never feeling good.