Diddy -- Your Baby Mama's a NIGHTMARE ... Says Ex-Nanny

Diddy's baby mama has pissed off ANOTHER nanny ... who claims Kim Porter treated her like crap and stiffed her out of some serious dough ... and now the ex-help wants Diddy's company to foot the bill, TMZ has learned.

Nanny #2 Amanda Jansen has filed a lawsuit in L.A. County Superior Court, claiming Porter hired her in 2011 to care for Diddy's children ... but her job quickly turned into that of a full-service round-the-clock housekeeper.

In addition to caring for the kids, Jansen claims she worked well over 100 hours a week doing all sorts of chores -- without ever being given a proper break.

Jansen -- who claims she was hired as live-in help -- also claims she was never given a room with a working lock ... had no furniture other than a bed and a computer desk ... and was forced to live out of a suitcase.

In the suit, Jansen claims she eventually complained about her crazy schedule -- and was fired as a result. Now, she's suing for overtime, wrongful termination, and more. Sources tell us she's looking for a 6-figure payout.

So why is Diddy involved? Jansen claims she was paid directly by Diddy's company, Bad Boy Worldwide Entertainment ... and therefore, the company should be on the hook.

You'll recall ... this is the second time Porter's been sued by a nanny in the last month. The previous lawsuit accused Porter of doing drugs around the kids, an allegation Porter denied.