It sounds like you are describing PVCs, or premature ventricular contractions. These are benign extra heart beats that typically don't cause major harm but can make you feel uncomfortable. Metoprolol can help suppress these extra beats, and if it's working but not completely, you may try a higher dose. There are other medications that treat PVCs, but they have a significant risk profile, so they are usually a last resort, and only used in severe cases. Lastly, there are procedures to ablate (burn) the location where the PVCs are coming from, but they carry a lot of risk as well.
The place to start would be to wear a Holter monitor to make the formal diagnosis and assess the PVC burden (how often you're having them).
There's no need to restrict your physical activity, because typically people experience fewer PVCs when they are active (faster heart rate leaves less time between normal beats for the premature beats to occur). The longer you're inactive, the more deconditioned you will get, and the more tired you'll feel, which won't be the result of the PVCs.
Thanks for the reply.
On Wednesday (June 12), I am going to my first rendez-vous with a cardiologist. It is going to be a discussion only. Kind of making me nervous.
I have never had a holter monitor. I have had ECG done when I went to the emergency during an attack on April 2012, then again July, then again December. ECG was normal.
Back then, I did not have hear pounding. Somehow, the December attack changed something.
I am taking bisoprolol now, low dose. 1.25 mg per day and I don't know if it is coincidence or the drug but the pounding went down. Feeling much better.