"Normal" HR depends on a lot of factors, but for an adult, let's say over 30 years old, a rest HR between 60-70 would be very good, and one between 70-80 would be acceptable, to me. Standing in the 90-100+ doesn't sound too high to me.
Given you have had the key tests by a board certified cardiologist (I assume), I'd next try to focus on the positive, not letting my mind take over and make the palpitations worse, that can happen. If this doesn't help I suggest you discuss again with a cardiologist.
I assume your test were: Echocardiogram and Heart Stress (not Nuclear) test. What about an EKG? You didn't mention that, and that is usually the fist test, before echo and stress.