Will Drinking Lot Of Cough Syrup Cause Late Period?

Hi..I last had sex on 2nd October and I got my periods on 19th oct and it lasted for 15 days on and off. Now I'm 22 days past my due date and no periods yet. I also took a home pregnancy test which came out negative. Am I pregnant? Is there a chance? What should I do? I travelled to India from US on 5th oct. I got really sick and was on medication for 2weeks. I had fever, cough and cold. I drank cough syrup(Ayurvedic) a lot to get rid of my cough. Is that the reason for missed periods? I was in the middle of my periods when I got sick, was the medicines a reason for 15 days of periods? I also have a lot of pimple breakouts on my face. I do get cyclic pimples but usually one or two. I don't know if it is because of missed periods. What should I do?