Credit: Brian Prahl/

Bump-y days and nights in Mexico!

Now four months pregnant with her second child, Kourtney Kardashian might not be ready to rock a bikini when summer 2012 hits.

But the reality star, 32, began a four-day jaunt to Mexico on Jan. 19 with beau Scott Disick and their son Mason, 2 -- and only the upcoming new Us Weekly has all the exclusive shots from the trio's babymoon.

Frolicking in the sand and surf, the eldest Kardashian sister showed off her expanding bump in a sexy two-piece from Beach Bunny.

As guests at pal Joe Francis' Punta Mita estate, Kardashian and Disick, 28, squeezed in couple time in between adventures with their little boy. "They were in complete family mode," a source tells Us.

Pick up the new Us Weekly -- on stands Friday -- for more exclusive photos and details from Kourtney's sweet babymoon!