Make sure you voice this to your doctor....I had been feeling the exact same way that you do...I went to the doctor and he said that sometimes anxiety attacks can magnify other symptoms you are already experiencing...I was diagnosed with rheumatoid arthritis....I can constant tiredness, stiffness, fatigue, nausea....And now that I am being treated for that...All is well!
My doctor also took me off prozac which is what I was on....And I use xanax when I need it for anxiety and panic. He switched me to buspar...Which is wonderful! No tiredness, no fatigue, and along with my ra treatments...And I take xanax when needed....After 10 years of suffering I feel like brand new!
Just make sure you don't hack up everything to anxiety....Check it out just in case! I could have been feeling alot better alot sooner if I hadn't just assumed my fatigue....Flu like symptoms...Joint pain etc was from anxiety...It wasn't! It just made me more aware of it!