I am presently taking 875 mg amoxicillin for an absessed tooth. I started on it last Friday (3+ days). I also have a sinus infection that I was hoping would clear up with the amoxicillin. It is not and I'm now coughing my head off and have heaviness on my chest. My dr previous prescribed azithromycin for me and I can get a refill. Can I take it with me already being on amoxicillin?