heart pounding very hard

For the last seven months, my heart has begun pounding hard when I wake up (either at night or in the morning), sometimes after meals, and after even mild exercise.  The beat is regular, not arrhythmic (although I used to have PVCs that went away a year ago). It beats so hard that it really frightens me. I feel it in my neck, sometimes the top of my head, sometimes my upper back, and sometimes in my chest. I also hear it in my ear much of the time.

I don't really have chest pain or shortness of breath, although I do have a tickly cough and mild aching some of the time (a lot of us ladies do  at age 69). And I get tired very easily.  I had a normal treadmill stress test and echocardiogram, plus a two day Holter Monitor several years ago (when I had PVCs).
The treadmill test and echo showed nothing but a little bit of mitral valve and tricuspid valve prolapse. Because of the heart pounding and fatigue, my doctor set up an appointment for me to see a cardiologist in three weeks.  

Three weeks is a long time, but it's the only appointment I can get right now. My regular doctor is wondering whether I might have coronary microvascular disease, which doesn't show up on regular tests for heart problems.  I may need a catherization or who knows what. Anyone out there have this condition? What is a catherization like?

Also, if you have heartburn or GERD,  how do you handle the stomach problems from beta blockers or calcium channel blockers sometimes given for that condition?.  My doctor has taken me off all PPIs like Nexium and H2 blockers like ranitidine or Pepcid, because I have such nasty side effects. Right now I'm just taking Mylanta cherry tablets for heartburn. Not working all that well. Sure could use some advice here.

[Madge270]

I should have added that when I have the heart pounding, my pulse is anywhere from 60 to 120 bpm, depending upon how active I've been. Pulse is usually not that fast unless I've been climbing stairs, etc.

My blood pressure, during the heart pounding is from 110-120/ 65-75 when resting, and from 155-132/75-79 when I haven't rested beforehand.  

I've stopped walking each day because the pounding drives me nuts and I get pretty worn out...need to nap.  Frankly, I'm kind of scared it might be CMD, because there's not much that can really be done for it. Too little is known, apparently.  Wish I could talk to someone who has it.  

I also have severe allergic reactions to antibiotics, so I get concerned every time I have to be in the hospital. Those places are full of bacterial infections, and I've nearly died several times from antibiotic allergic reactions.