The pregnant actress, 31, proudly showed off her belly in a skimpy two-piece in Mexico on March 6.
Vacationing with son Ryder, 7, and beau-turned-baby daddy Matthew Bellamy, the actress, 31, soaked up the sun in Cabo.
"They are really happy," a source tells Us of the couple, who started dating after meeting backstage at the Coachella music festival in Indio, California last April.
Still, the "Something Borrowed" star, due this summer, isn't quite ready to wed the Brit rocker, 32. Her focus? Prepping for baby No. 2. "Kate is happy for Ryder to finally have a brother or sister," says a friend. Adds another insider, "she's a great mom."