Sounds like the meds.

I don't know what you're doing now, but you might try increasing physical activity. Drinking more is good - well, if it's stuff like water, sugary stuff might make you more tired. Water will flush out your body - a good thing for anyone - and help keep you hydrated, particularly if the meds are drying you out. And try to keep a balanced diet, as too much sugar/carbs will tire you out if you're not putting them to use, and a balanced diet will help you naturally feel better.

If it's safe to take a walk before bed, or if you can find someone to go with you, (walk a dog?) it may help you sleep better, and with less nightmares. Also, getting out in the sun (with proper skin protection) is a natural brain chemical booster - which is why many sunbathers feel happy and fall asleep while lying out. Some sun intake would probably be good for you, too.

Aside from feeling tired, is your mood any better?