Gently op, you don't owe this man anything, not even an explanation.
You should block him today. Now. Just do it.
Then take some time to think about what has happened over the last month. You've met a total stranger who has utterly love-bombed you, persuaded you into unprotected sex putting your health at risk, probably lied to you about his fertility and family circumstances.
Even if he was the most amazing man on the planet I'd be wary of his family - that alone would have me running for the hills.
If you have a child with him you will be tied to him and his crazy family for the rest of your life.
You owe him nothing. Block.