story courtesy TMZ

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.