Lexy Panterra will soon be welcoming her first child … because TMZ has learned she’s pregnant — and she’s got no issue showing off her growing baby bump.

Check out these pics of the star from a New York Fashion Week event Friday night … where she wore a button-down shirt — then popped the buttons to let her tanned tummy breathe.

We’ve learned Lexy is 5 months pregnant … after marrying her mystery fiancé back in February — another bombshell revelation. She’s still keeping his ID a secret … apparently he’s a super low-key dude.

While she could just be taking it easy — after all, she is growing a life inside her — Lexy jumped up to perform her hit song “Girls” at the event … getting the crowd rocking to the beat.

We broke the story about Lexy’s engagement … sharing the moment he got down on one knee in a heartfelt video last year — while she was trying on wedding dresses. She said they’d already discussed tying the knot prior to the proposal, hence the dress shopping.

From engaged to pregnant in less than a year … time flies when you’re in love.