Potty training help - 💩

My son has been potty training for a month now, and is completely PEE trained, but when it comes to poop, he always poops in his pants, and THEN runs to the potty and sits down before crying that he pooped his pants.

Does anyone have any suggestions on how I can get him to poop on the potty? When he first started training, he pooped on the potty twice, and we made a massive deal out of it.

He’s 3 in September, and has a slight speech & language delay. Also, we’ve tried signing, it’s no good for us.