Need to find out about employment labor laws!?

I need to find out if an employer can keep you from going to doctor when needed. My husband has had problems with pain in his back from infection called H. Pylori in his body for the past 4 months just now we have found out that it could be this infection. However, he drives a soda truck and we have been having problems out of this employer for awhile but due to not hardly any jobs around here he has been holding onto it for awhile. He can't even take his children to the doctor when they need to go because his employer claims that his job should come before them. I take epileptic seizures he isn't even allowed to take off if I was to have one of my episodes. There has to be something out there saying that an employer can't keep an employee from being off work if he/she is sick or is following doctor orders and if a family emergency goes on! Someone please help!