Why wont my betta fish poop?

i got a red male crowntail betta 2 weeks ago and i havent seen it poop once. i look in the gravel and dont see any poop. but i do see little white slivers in the gravel but i ume that is just leftover food. he is happy and healthy he makes bubble nests and my name is danny and one time he designed the letter D with a little heart before it i thought it was cute. hes active but he usualy lays at the bottom of his live plant sideways but he swims often. so why isnt he pooping???!!!!!???? i fast him 3 times a week and i still never see any poo. i feed him betta min flakes most days on others i feed him pellets, and some days i feed him bloodworms. i feed him twice a day exept when i fast him. his temp is always around 80