Have a pulsing sensation in the middle under my rib cage. my pulse is normal and i feel fine i have just never felt this before. ?

Probably the aorta: The abdominal aorta (big artery from the heart) can often be felt, especially in thin people, right underneath the rib cage - in the midline ("solar plexus"). Unless it is enlarged, there is usually nothing to worry about. It may be hard for you to tell if it's enlarged, but given your age, I doubt it is. Talk to your doc about appropriate tests. And don't smoke! (most common reason for big aorta)