My belly has a pluse. Help?

I'm 16 years old. At a healthy weight (not super thin or over weight). And besdies asthma, exzama, and allergies, I'm healthy. Over the past few months I've noticed my belly pulsing on the left side next to my belly button. It pretty much just beats along with my heartbeat and pulse. I've done some reasearch and I've read things about aneurysms but it's said to involve pain. I have no pain, just the pulsing. My hands and feet have also been extremly clamy lately. If you have any idea what this may be could you please help? I would just like to know if I should be worried or what it may be.