Why does my baby daddy care who I date?

So, my baby daddy always tells me that he wants me to be happy but when I meet someone new and begin to move on. He messages them and tells them that I am crazy and if I was such a catch he would still be with me. They eventually get scared away and start ignoring me because they do not want to deal with baby mama/ baby daddy drama. Then he says, "see nobody wants you because your a worthless whore". I don't get why he does this, if he doesn't want me that why won't he let me move on? Recently, I started talking to one of his mutual friends and he did this. He went as far as telling his friend that if he dates me he will date his friends baby mama, and that I didn't actually like him and that I was just trying to date his friend to get back at him. He keeps telling his friend that he is not his real friend for wanting to date me and begging him to not give me a chance but in person he says he is happy for us.
Why does my baby daddy care who I date?
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