BeatNik

Hi!

Recently I've become abit concerned over my heart due to a number of reasons and I know these boards are a wealth of knowledge and experience, so I thought i'd ask here .
Firstly, I'm 18 - up until recently I've lived an active lifestyle, including taking 800m running seriously. I am not unfit and walk everywhere... including to school and back every morning and every evening (a very fast paced 25 minute walk). I'm known to be always running to various places, and I also dance alot on the weekends. (about 6 hours average of what feels like very good exercise)
I also have Gilbert's syndrome (if that is relevant)...

Recently however I've realised that my heart does beat very slowly, when I lie down for about 5 minutes I can usually count an average of about 50bpm (between 47 and 55)... and even when I'm sitting and have been moving for a while I have a rate of about 60.

I haven't been worried though until recently, when i've not only feel my heartbeat more powerfully than before (i actually feel my chest move when my heart beats) but I also have had sensations of very short but strong dizziness (about half a minute to a minute each) and feelings of falling. I also have sensations of chest tightness and pain as well. Sometimes I feel very anxious, but at other times I do not, these things sometimes happen even when I sit by a chair.
I also get this falling sensation very powerfull when I lie down to go to bed, and wakes me up from being almost asleep.
I have smoked quite abit before (started too young and was far too foolish), but have recently stopped... And due to that have used nicotine chewing gum. I have also been under abit of stress recently.
My blood pressure is apparently not high or low at all...

Do you think that it's something that I should be concerned about, or could it merely be a product of something else.

Any help would be hugely appreciated...
All the best to all of you

Nicko