Aww Jen, you're really not having an easy time of this, are you? That really doesn't sound like fun.
I've had occasional, very brief, feelings like my heart has skipped a beat, or had an extra beat (it's hard to tell exactly what happens- I can just tell that something went wonky). But I'm not sure if it's actually my heart, or just anxiety or heartburn or something.
I've been told that heartburn/reflux type problems can cause feelings that feel like cardiac symptoms. Since you mentioned burping, perhaps you should look into that.
But I wouldn't hesitate to go to the ER, if I were you. Better safe than sorry. You don't want to mess around with your heart.