i'm not a dr. but have had many thyroid problems. (many!) which can be very frustrating. yes, being tired and sluggish is certainly somehing that comes from being hypo. other things that can happen are dry, itchy skin, being pale, gaining weight, feeling a little depressed longer menstruation etc. I'm not sure if there is any diet or excersise you can do, from what i understand your thyroid just works or it doesn't. but the good news is, they will probably just give you a small pill to take, and you'll start to feel better pretty quickly.
Best of luck!