The pop star posted a clip of herself at the crib Tuesday, where she was spinning around to some earthy tunes playing in the background. Nothing really new there -- except this time, she started weeping toward the end ... kinda out of nowhere.

Now, it appears BS knew people might be alarmed by her crying, because she got ahead of it ... noting in her caption that she was not having a breakdown here, per se, but simply letting out emotions.

Brit said, "It’s been a while since I’ve cried on camera !!! It’s not a breakdown assholes, it’s a release that I’ve needed for a very long time now !!! Spiritual experience for sure !!! I think I need to do that way more 🌹🌹🌹 !!! Psss… bawling."

Unclear if Britney was moved by the music/dancing ... or if it's related to her conservatorship, or even both. What we do know is she's aware there are more eyes on her now as she continues to feud with her sons ... while also taking shots at contemporaries of hers, like Christina Aguilera -- who she kinda fat-shamed this week.

You might've heard about this one too ... Britney posted a quote from Rodney Dangerfield on IG that read, "I found there was only one way to look thin: hang out with fat people." She furthered that thought by name-dropping Christina and her backup dancers, saying if she had those same peeps in her orbit during the peak of her fame ... she'd look "extremely small."

Britney caught A LOT of backlash from that, with many taking it as body shaming ... but she defended herself in a follow-up post by insisting she wasn't trying to put anyone down, and that she'd been misunderstood. In any case, Christina unfollowed her as a result.