My son was up all night with a croupy cough and he also has asthma. Could that be the reason why or could it be something else?

See below. The croupy cough could be classic croup or it could be an exacerbation of the asthma. There are other factors that could help distinguish the difference such as fever, wheezing and chest tightness. You did not mention your sons age but that could also alter the causes. If having difficulty breathing he should be seen by doctor.