Hello and welcome to HCM
I have read your mail in detail. Your palpitations might be due to Iron deficiency anemia
or due to anxiety
or due to both the factors. Palpitations can also be causes due to heart related problems but it seems that you are not suffering from it as you are already on beta blockers.
Consult your doctor and start treatment for Iron deficiency and for anxiety just be relaxed and have some time with your dear ones. If does't work can start medication for anxiety also.
If you want to change your beta blocker than you may shift to calcium channel blockers but consult your doctor before altering it.