I feel like this very often. I will feel perfectly normal & then out of the blue I will feel my heart start to pound. It scares me to death every time it happens. You would think that I would get used to it after a while, but it still scares me. Since I have been taking the medicine, though, it never (or hasn't yet) gone into a full blown attack (thank goodness!). Hang in there. We'll get through this.
P.S. I just want to say that I am so glad I have found this site. This is only my second day to be on here. I have felt better than I have in months since I have read through this site. Thank you all.