A resting heart rate
over 100 is not normal. So is 200 on mild to moderate effort.
Your doctor is doing the right things - Holter (24-hour ECG monitoring) is a must to throw light on your condition. You will also need to have some blood tests - Thyroid
function, for example. The proper treatment is based on the results of investigations.
I suggest you take off from your work - physical and psychological strain may contribute more.
Have a friend or relative fully informed - and what to do, whom to approach in an Emergency