Why can i feel my heart beat in my stomache?

Aorta: The aorta comes out from the heart towards the head and then curves around to go down to the rest of the body. It travels alongside the esophagus and past the stomach and intestines before it bifurcates and supplies the individual legs. Thin individuals in particular may be able to feel their pulse from the abdominal aorta in the stomach in certain positions or if their blood pressure elevates.

Thin?: Aorta, major artery going from heart passes through abdomen feeds gut, etc. Thin people may feel pulsations. Unlikely at your age but abnormalities of aorta (aneuryms) dilations can cause pulsations that you can feel, either with your hand, or less commonly internally.