Question about my allergies?

I am on allergy inj, and singular everyday, and I guess it's the weather nowadays but my sinuses are all congested and all and it's been about 3 days, and I know to wait a few more days to be sure, but I am already on singular, and am working the next few days and can't afford to be sick. Normally it's always a sinus infection with me,,So I was wondering if I can go ahead and get an antibiotic or would that harm me if I don't wait?