You and the Dr treating you are absolutely right. Mononucleosis
may not present with all the symptoms. If the Dr has diagnosed it as mono then it is best to avoid contact sports. Your routine exercises can be done provided that they are not too vigorous and make you strain.Listen to your body and make sure you eat healthy. Take it easy for a week and then you can get back to normal.
I hope you found my response to be helpful and informative. If you have any additional concerns I would be happy to address them.