Last November I started experiencing spells where my heart would race so fast that I could fill it in my throat and it would almost choke me or make me want to cough.

I'm so sorry you've suffered miscarriages. It might be panic attacks like you said, but something stood out in your post about how you feel like you need to cough. I occasionally get irregular heartbeats and I've had them checked and they're the non-threatening kind. But when I get them, I can feel my heart skips a beat and I usually get the urge to cough. Have you had your heart checked? They can give you a 'halter monitor' to wear at home for 24hrs. All it is is a box you wear on your belt with electrodes attached to your chest leading to the box. When you feel it happening you push the button. I just want you to rule out any heart abnormality. I also recommend having your thyroid checked and watch your caffiene intake