The actress showed off her pregnancy progress Wednesday, plus the room she's preparing for her kid.

Lindsay says she designed the nursery with Nestig, a furniture and decor brand for little ones, and she's drawn inspiration from the beach.

TMZ broke the story ... Lindsay's pregnant with a boy -- and, as you can see, she's going kinda traditional with a mostly blue decor.

Looks like Lindsay's kid will be chilling with a huge teddy bear and a sweet crib once he arrives. We don't know her due date, but considering she announced the pregnancy back in March ... it's a good bet she's into her third trimester.