Sinus Medication Solution

I have had what I think is a minor sinus infection for nearly a week now and have spent the entire week, very tired. I sleep well at night, go to bed early and am still exhausted all day long.Any ideas what else it could be? (my symptoms are stuffy nose/head, headache, nasal blockage, dry cough)

I try to fall asleep but end up staying awake until the about 3 am when i go to bed at 11 pm.My doctor perscribed it to me because I have a sinus infection. Is this unusual that is almost acting like caffine?