Hey Suzan
That sounds like anxiety to me. I have dealt with anxiety and panic attacks for a couple of years and racing heart and just that pounding palpitation sensation is a symptom of high stress and anxiety. Your heart is probably really not racing it just might feel like it is pounding because you are more aware of it right now. Do you feel like you are very stressed or worried right now? Even if you are not conciously worried at the moment your body can still send out symptoms even if you aren't thinking or worrying right at the moment. I do know though that the more you focus on a symptom the more pronounced it will seem and the more it will affect you. My best advice with the racing heart is to just ignore it the best you can and it will go away. And then try to figure out ways to deal with your worry/stress. Exercise and deep relaxation really help me.
Of course there are some medical reasons for racing heart and if it continues and causing you discomfort you should probably talk to your doctor. But in my humble and not so professional opinion

it is probably due to stress. It is common for women to experience lots of anxiety/stress symptoms after a m/c. (someone posted a great thread re: this a couple of months ago---I'll try to find it). In my experience, after my m/c in Oct I've had lots of anxiety and I had been doing great prior to it. The fluctuation of hormones contributes to this alot I think. Staying away from caffeine and sugar helps with this too.
As far as this affecting conception I really don't know. I have read that stress can have a negative effect on getting pregnant which I would believe that to be a survival mechanism in order to optimize the growing environment of the fertilized egg. But who knows....
So relax and don't worry and take advantage of your O tomorrow