Toprol-XL and correlation

Been on Toprol XL for 4 years. I am 64 with SVT and mitral valve prolapse. I was started at 50mg daily and got relief but when breakthrough SVT started the dose went up to 50mg in the AM and 25mg in the evening. I still have breakthroughs but can wait them out. I did notice that my SVT or palpitations seemed to be triggered with an imminent BM. I have been diagnosed with fibromyalgia but coincidentally....it started with severe muscle pain when I started taking Toprol XL. I wasn't told that this could be a side effect.HMMMM When my insurance was discontinued (retirement) I started taking the generic due to cost. I haven't noticed any difference between the two. I also noticed that after a SVT episode I have a increase in urination....Toprol or SVT? I also noticed that I am very aware of an increase in a feeling doom. I have had ekgs etc and my heart is in good shape otherwise.