Does Taking Digoxin And Betablockers Cause Tiredness And Pressure In Arms And Chest?

Hi I have been taking digoxin and betablockers for 4 weeks because I was diagnosed with atrial fibrilation ( I suffer from a heart condition and awaiting surgery for the replacement of 2 valves). I have noticed that when i take the tablets mentioned above I become very tired and can't walk . I also feel a sort of pressure on my arms and my chest. But today I wanted to make an experiment so I delayed taking the tablets, so when I went out I felt better than yesterday.
Could you please tell me if the symptoms are due to the medication and whether I should take the medicine later in the day thank you in advance for your advice and time