hard beats and light-headedness

Just wondering if any can relate to this experience, or maybe give an explanation as to what they think might have happened...
So, as my other posts indicate, I have been experiencing A-fib as of late and am currently on Bystolic, very low 2.5mg dose. I've been on this med for almost two weeks, and have had a much better experience with it than I did on metoprolol. So far, I don't think I've felt any fibbing at all.
Last night as I was getting ready for bed, I started to feel flush/hot in the face. I took my bp and pulse rate, but all was normal (117/79, 71). Then I started to feel "swimmy" in the head, not really dizzy, but very odd. So I layed down and the feelings in my head persisted, and I started to feel even more jumbled. I took bp and pulse rate again, and all was still normal. I was laying on my back then, and felt two VERY strong heart beats in a row, then got light-headed. My breathing felt a little short but not seriously affected. I kept trying to lay down and sleep for a while, but couldn't shake the murky/swimmy feeling in my head. I eventually dozed off, and woke this morning feeling alright.
Anyone have any idea what this could be? Nerves, fibs, etc?

thank you! this is extremely helpful, and does explain a lot!