Why is my husband feeling like this?

Your husband really should see a doctor. Lots of medication can cause stomach problems and it can happen after you have been taking the medicine for a short or long period of time. Symptoms can be anything from feeling bloated to raging indigestion and reflux. At worse he could develop an ulcer in the short term. But whatever is giving him these problems needs investigation. At this moment in time all he probably needs is a course of a proton pump inhibitor medication.