Toprol-XL and going to the bathroom

I started taking the generic of Toprol (metaprolol) 3 months ago. I'm on 150mg per day for a rapid heartbeat, I'm 39 years old. It has helped my heart problems but I don't know if the side effects are worth it. I experience major fatigue that may last a week at a time and subside for a few days, aches in my back and neck (which I've learned may also be attributed to the Lipitor that I am also on), and my worse symptom is constant diarrhea. Some days I will run to the BR 15 times in one day. It seems to subside by dinner time, but that is probably because I stay away from food all afternoon. I'm fortunate that I am a stay at home mom I can't imagine having to go to work in this condition!