I don't mean any disrespect towards you or your boyfriend, but...well, how on earth did he intend to keep the baby secret once born? That seems...odd, to me.
At any rate, I am sorry.

It is absolutely unfair of him to "make" you choose between your family and him, and honestly incredibly childish. You don't need stress like that during your pregnancy.
It's not his place to make you choose...a stable relationship doesn't work like that. If I were you, I would tell him that. How would he feel if put in the same ultimatum?
I hope you two will be able to work this out, and congratulations on becoming a parent!