Trying to potty train a 20 month old. He either takes the pull up off right after go or before & go on floor?

How can I stop him. He just crapped and it's all smashed in my damn carpet. I'm so mad. I'm happy he tells me but this going on the floor is getting old. He do use the bathroom sometimes. But times he don't wanna tell me. He will go to the bathroom but i keep the door close because he will go in there and pull all the toilet paper off the roll, Play in the toilet or lock him self in there. help me