What Really Causes Bloating? I Have Experienced This For About

What really causes Bloating? I have experienced this for about a year now. It began after I was prescribed Metoprolol after being diagnosed w/Tachycardia which resulted from a side effect of chemotherapy for BC. Due to side effects from Metoprolol I am currently on Varipamil 1/4 of 60mg daily. I also take Simastatin 10 mg daily. I never had a problem with bloating until I started taking the beta blocker Metoprolol. I always a flat stomach. I need to know what I must do to get rid of the bloating. Please any suggestions.