My 3 year old DS has had a nasty cough for just over a week. We hoped it had cleared up but it seems to have got a bit worse over the last day or so. On Saturday he coughed so much overnight he was sick a couple of times. He coughs during the day when he exerts himself even in the slightest way, like today when he was dancing. He seems happy apart from being a bit tired, no temp and breathing ok. He did have a cold but that's gone. It's much worse at night. He had croup last year so I know it's not that. We have a doctors appointment on weds so they can check him over. I keep worrying it's asthma as he is prone to coughs. How long do these coughs usually take to pass?