12:35 PM PT --  Sources with direct knowledge tell TMZ ... Hailey Bieber's a little over six months pregnant, so sounds like she's entering the third trimester soon and we might have Baby Bieber by late summer!!!

Justin Bieber and Hailey Bieber are having a baby -- something the couple just announced ... and it looks like Hailey is somewhat far along, 'cause she's got a bump going.

The Biebers just posted the same thing -- a carousel of pictures and videos that show them engaged in a photo shoot out in a field somewhere ... with Hailey dressed in white and showing around her midsection.

There's no caption for either of the IG posts ... all they did was tag each other, but the message is clear -- they're expecting, and they're over the moon about it.

In the video ... Justin and Hailey can be seen smooching, and in the accompanying photos, it looks like Justin was playing photographer during the pregnancy shoot. It also looks like they might have renewed their vows during this ... 'cause his pastor is there in the mix as well.

Remember ... the last time we saw Justin and Hailey together was a couple weeks ago in Hawaii, where they popped up looking cute and happy. People noticed that Hailey was wearing a flowing, loose dress ... and some speculated she might've been preggo then.

Now, we know she 100% was ... a secret that was well-kept. Also ... this might explain why Justin recently posted selfies showing himself crying -- with this news, it would appear those were tears of joy.

They've been married since 2018 ... and we know they've talked about wanting kids and trying for a while. Now, it looks like they got one coming ... get ready for a baby Bieber, y'all.

Congrats!!!