Due to fever my 5 month old has been refusing milk for the past 7 hrs, he kept wanting to sleep, what shuld I do?

Have them seen. Would call local family doctor or pediatrician and discuss with them. If they cannot see baby would go to er in preferably a children's hospital if available. Babies under one year old with alterations in behavior and possibly level of consciousness should be seen quickly.
Liquids. It is more important the child is drinking fluids than it is to consume milk in the first 24 hours. If you try juices or water and the child is also refusing then i would have the child checked to see if he or she is having pain when swallowing.