My Doctor Toke Me Off Metoprolol Tartrate 100 Mgs 2

My doctor toke me off metoprolol tartrate 100 mgs 2 times a day, on thursday and I started cardizem cd friday and i am now not feeling myself. I feel as if my heartrate has went up with activity and i can really feel my heartbeat in my chest. I feel a little anxious also. Is this normal being that I stopped a medicine one day and started a new one the next? will this feeling go away once the new medicine gets in my system good or maybe could the dose not be enough...Im just worried a little...I am on the medicine for palpatations and a possible rhythem problem.