Hi i read your post.....there to me is nothing like the feeling of a fib when you go into it.....your heart takes off like a race horse. Sometimes right before it starts you may feel a funny feeling in the neck area and then boom off it goes. You can look down and see your blouse/shirt moving up and down because your heart is beating so fast. I went thru alot of different heart problems and had them corrected thru an ablation 3 years ago but a fib is a little thing i will never forget....medically speaking they say true a fib begins when your heart gets up above 140 beats per minute and unfortunately i was one of those unlucky ones that a couple of times mine went into the 300's. Very very scary.....a fib is not so much an irregular beat if that is all that you have but an incredibly fast one and as far as the flutter goes it sort of feels like a little bird inside of your chest flapping its wings....the strong thuds you feel in your chest may very well be your heart attempting to go into a fib but your electrical pathway is not allowing it to happen and for that you are lucky......if in doubt and you are noticing something different that you haven't felt before just make a call to your heart doc for a little reassurance....good luck
I just wanted to add that I doubt that you have A-Fib because I had AVNRT and I had what you had but don't listen to a lay person go find an electrophysiologist they are the ones that can diagnose often from an EKG.
I had a lot of trouble with my heart rhythm during pregnancy as well. Ended up I had AVNRT and I had an ablation for it a week ago. So far, so great! Pregnancy pushes the baby up against your heart and if you have any underlying issues that's when they often surface. I had only what you had during the pregnancy but after delivery when my hormones went back down I ended up with a heart rate of 250 and they had to bring it down. Hopefully yours is just a fluke but I would check everything out with an electrophysiologist not just a regular cardiologist. A regular cardiologist was never helpful to me. Best Wishes.