Potty training

So he always says before he poops: “poop coming” and if he wants to pee he will say: “oooh pee!”. Then he will just stand and poop or pee in his diaper. Then he will remove the dirty diaper saying : “diiirtyyyy” and ask for a clean one. We of course tried to put him on potty, on regular toilet, on boy’s potty, with diaper, without diaper, he gets scared and says: nooo, poop no, pee no. And he will get up. How can he be so ready but meanwhile so not ready? 😀 any ideas why can he be so scared or how to help him? 😳