Infant cough cold...?

My son just turned 2 months old. He has had a URI since july 4th and now it is starting to get worse instead of better. He will cough like 5-10 times in a row then not cough for 30-40 minutes and then cough 5-10 times again and now his coughs have like a whistle at the end. i dont want to immeditaly jump to whooping cough but they did test him for that and i should have the results back by friday i was just wondering what else it could possibly be.