Hi Melissa
Sorry to hear about your distress. As others have said, of course get checked out by a cardiologist. If all turns out well there, then do not dismiss anxiety as a major factor.
In my early thirties, amidst raising children, I had palpatations badly and always at night. They would occur after the kids were all in bed and when I was laying down trying to fall asleep. One time they were so bad that I ran out of a motel room, down the hallway and out the door. I would feel as though my heart was pounding and I could not get enough breath. Once I even went to an all night drug store and bought an OTC inhaler.
I suffered with them for a few years. Then I finally did some research on my own and found that this is a fairly common occurance for women around 30. It has a lot to do with the amount of responsibility we face at this time in our lives. With that knowledge, I investigated some techniques (like the cold water things) and found a large degree of relief.
I wish you well
reach