My boyfriend wants to have a baby by someone else?

I dont know why but im pregnant and he's now telling me that im his main chick and i've earned my thrown but at the same time he says he wants 5 kind 3 by me and 2 by someone else.... At first i thought he was just playin but now i see he's telling th truth... What should I do? Should I leave Him? I don't wanna be a stepmom and Im so confused!!!!!!!!!!