Why would he do this to me?

So my boyfriend baby mom just given birth to his child almost a month ago. He hasn't been around their child because i don't want him to be. But anyway, yesterday i went through his phone and seen that another female send a picture of her pregnancy test which was positive. Smh. He keeps on saying that She's lying and that he don't know the girl. This is the same thing he said about his baby mom. I begged him to leave his baby mom alone just to end up seeing another female pregnant by him too. Why would he do this to me? And it's sad because we don't never use protection.
Why would he do this to me?
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