Halle Berry PREGNANT with baby number 2

Halle Berry is pregnant with her second child ... TMZ has learned.

Sources connected with the actress and her fiance, Olivier Martinez, tell TMZ ... Halle is around 3 months pregnant -- based on the pics and some other facts we know ... she may be a little further along.

What's more ... they know the sex.  It's a boy.

This could explain why Halle and Olivier were so upset when paparazzi got too close to her earlier this week at LAX while she was carrying soon-to-be big sister Nahla, who is 5.

It's definitely worth noting ... Halle is 46, and Olivier is 47.

Source:TMZ