hi there :)
boy, i sure do know how you feel. i wont give any advice that should be worked out by a doctor but i will share how i have dealt with extreme tiredness.
my doctor worked me up for some common culprits, thyroid, blood iron, and other labs. certainly meds can and do cause tiredness, often too, it can go away after a few weeks.
to try to stay somewhat on top of the game, i have to eat well, for me that means healthy snacks and more but smaller meals througout the day...
also hydration...more fluids in your body means higher blood volume, means you feel better...
and the absolute must is exercise for me. this is so hard because how do you get out and run (or hike, walk, whatever) when you dont feel up to anything?? for me the only answer is, you just do, like you just do take your meds. if i miss a day, i feel pretty bad. i feel pretty bad before and while i drag myself out for my runs, in fact i fret all day because i dont think i can do it, but once i do...phew...feel so much better....
--sorry if kind of ramble-ly--
good luck to you!!!
elaine