arrythmia

Now Im taking 25mg of antenolol a day and feel alot better from taking 12.5 mg but still getting extra beats and rythem problems with the heart.  Seems to happen before my menstrual wich is weird to me.  I would say the medicine is helping it, but when I excersize or go swimming I notice I get them more the next day, and its all day long, extra beats.....but without the medicine it would probably be alot worse....Now the doctor wants me to up my medicine to 50mg of antenolol but my bp is already pretty low its at 110/55 bpm is 60.  but he wants me to take it twice a day instead of once a day he said that should help your pressure from going to low, but I disagree because before I took any medicine my bp was 120/70 bpm 85 now it went down alot....So, I don't know if I should take the medicine and see what happens and hope for the best! Wasn't for the arrythmias that Im experiencing I would leave my medicine at 25mg a day but now with this problem he wants to up it....to 50mg a day....What to do?