My son and his asthma

I am not sure what is going on with my son but he has been having a lot of attacks lately. Actually, I know what is wrong with him. He had a cold this last week and when ever he catches one he has breathing problems. Last wednesday he started have a lot of trouble at night and I had to give him his breathing nebulizer treatment a few times. I hate it when he has breathing trouble. I feel so bad for him because he gets real scared sometimes. :o(