Hihi congrats on your pregnancy! Baby's heartbeat cannot be felt externally & its way faster than our own. Its most probably your own pulse, we have arteries running thru our stomach. I have noticed that even before I got pregnant, bet you r noticing your tummy more coz of baby. ^_^ dont't worry about it, you might be able to feel baby kicking and turning around at around 18 weeks when their bones grow stronger. Take care, eat well & maintain positivity! Enjoy your pregnancy. Cheers!