Hi, may I answer your health queries right now ?  Please type your query here...When laying flat on back I can feel a long hard mass about half an inch above and below my belly button, this mass has a heartbeat like pulse and is not tender. What might it be?
Two possibilities are there in this case: benign vascular lesion like hematoma and hernia.in worse case it could be some tumor or tumor-like condition. Kindly get immediate physical examination by a general surgeon; USG/Doppler study could easily pick it up!get well soon!