My heart doesnt flutter, but I do get rapid heartbeat a lot. And the more I focus on it the faster is seems to beat. I think I make myself more nervous. I have Panic disorder and OCD as well. I get nervous over every little strange feeling I have. Then I start thinking something is wrong and my chest gets real tight and I feel like I can't breath and then I panic.
I'm sure what your going through is just panic/anxiety. If you are really concerned, you can go to the doctor just to make sure. That way if it happens again you know it's nothing to worry about.
28 Years Old - Suffering from Panic Attacks since I was 18
Diagnosed w/ Panic Disorder, OCD & Bipolar II
Prescribed 25mg Lamictal every other day - will increase dose gradually