Cardi B's taking recent reports to task ... claiming she doesn't know who's saying Offset hasn't supported her -- 'cause it can't be anyone who really knows their marriage.

The rapper responded to a widely shared story going around claiming Offset never supported her during their marriage ... dropping an Instagram comment denying that was ever the case.

According to CB ... Offset helps out a ton with her business and their kids -- and, she says she's never sent family or friends to speak to the media on her behalf, so she's got no idea who the reports are citing.

Cardi even points to her divorce filing ... saying she's not asking for any child support -- she just wants Offset to keep making the payments for their kids like he has been 'cause he always pays his share.

If you haven't seen the report ... an anonymous source is claiming part of the reason for Cardi and Offset's divorce is that she didn't feel supported. The report Cardi cites -- from People, who she namechecks in the comment -- has since been amended.

As we've told you ... Cardi filed for divorce this week, right around the same time she announced she was pregnant. The documents confirm this child is her third with Offset.

She's seeking primary custody of their children ... and, asking for child support to boot -- erm, wanting Offset to keep making payments for their kids we should say -- but, all indications say this is an amicable split.

In fact, our sources say this divorce came from two people who just drifted apart over time ... and infidelity did not play a role in the divorce.