He sounds like a complete dick to me. Sorry if me being so blunt upsets you, but seriously, getting you pregnant at 16, getting engaged to you, then dumping you 'cause of something you did but didn't do (if you know what I mean) is bullshit, especially seeing as he got a BJ at the same time as you getting with this other guy. If he thinks that's all fine then he's a dick and don't deserve you.
Either have an abortion (if you're able to/if you want to), or have the baby and look after yourself and the little kid because it's father's a complete twat.

Once again, sorry for being blunt, but I can only go by what you've written, and you described him as a complete twat.

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