I am a 26 Y/o mostly healthy male. I am technically obese but only just barely..currently losing weight. I am a non-smoker. I recently noticed a pulsing in my abdomen. As far as I can tell, it always becomes noticeable after large-ish meals (a normal 700-800 calorie usually produces it). Its very noticeable lying down, and occasionally noticeable when standing. I have no significant pain to speak of in the abdomen or back. I had pain in my left breast which went away (heart was checked, seems to be okay), I have lingering recurring pain in my left shoulder and left rib cage. My doctor thinks the pain is anxiety related (I have/had a panic disorder, i had continuous panic attacks for 3 months nearly daily, they have largely gone away over the last month).
The video below shows the pulsing. I recommend viewing from 38-48 seconds specifically. At 38 seconds i inhale (which causes the single large pulse). Afterwards you can clearly see, a continuous pulsing. The pulsing is exactly in tune with my heart beat. Pressing my hands above my belly button, i can feel my aorta pulsing, but I have no idea if it is pulsing "normally" or abnormally. The pulsing does push my fingers back slightly, but i do not know if I am pushing hard enough for this to be diagnostic.
https://www.youtube.com/watch?v=RAn6ordP4k4