@rogerchua
Assuming it’s not just allergies, consider sudafed 12hr in the evening to dry out your sinuses overnight. I’ve had something similar a few times in the past and it can take several days or more to clear up. I suspect it’s an almost-sinus infection process underway. Some people sleep poorly on sudafed though, if that’s you maybe try a phenylephrine pill or spray instead (similar drug, just not as good).
@jhow
My sinuses have been very bad for years. I strongly recommend Afrin the night before a race, and possibly an extra dose day-of. Afrin is incredible. Try not to use it chronically.
-general
I don’t have asthma (at least that I know of), but my pcp had suggested singulair as an attempt resolving my chronic sinususitic. Didn’t help my sinusitus, but I did feel like it improved my breathing a little on races (cyclocross: cool/cold/damp). I did some reading and apparently there’s an exercise-induced-asthma, and maybe I have a little of that. Not sure how if it’s contraindicated with any of the more serious prescription inhaler medications coming up in this thread, but could be worth a discussion with your doctor if most symptoms occur during exercise.