I have a sinus inf this is the fifth day on avelox q d. Should I still feel bad?

Sinus Infection. Most patients get "better" by the 3rd - 5th day after starting avelox. But, if the sinuses are still clogged up, the pressure may persist. This assumes most of the symptoms are due to the presence of a bacterial infection. Add an oral decongestant, or best add afrin, (oxymetazoline) 2 puffs / 2 - 3 times per day, for up to three days. Afrin (oxymetazoline) is addicting, if used longer than a few days. Don't continue the use.
Possibly. If the sinus infection is bacterial, the Avelox should do the trick, assuming the causative "bugs" are susceptible to avelox. Sometimes infection takes full course of antibiotic to clear. However, the infection may be viral, in which case antibiotics don't work. Try salt-water nasal spray and a decongestant to relieve pressure & promote drainage. If getting worse, see doc again for re-evaluation.