Oksana Grigorieva Sues -- My Lawyers Screwed Me in Mel Gibson Settlement

Oksana Grigorieva says she was sabotaged by her own lawyers in her settlement with Mel Gibson -- and wound up with a TERRIBLE custody agreement ... and now she's suing.

TMZ has obtained legal docs, filed by Oksana herself (without a lawyer) ... in which she accuses Ron Litz and Daniel Horowitz of negligently advising her to sign off on a bad deal back in 2011.

According to Oksana's lawsuit, the crappy deal she signed forbids her from pursuing any future legal action against Mel regarding their child without jeopardizing the monetary settlement she made from the actor. And as we all know about Oksana ... she LOOOVES to take legal action against people.

As part of Oksana's deal with Mel ... the actor had agreed to pay Oksana $750k in cash ... PLUS provide a house for Oksana and their daughter Lucia until Lucia turns 18.

Oksana says was also advised to sign a legal document that divested her of all ownership rights to her house ... a document she claims she never would have signed if not for the lawyers.

Oksana is demanding unspecified damages.

We spoke with Horowitz who tells us, "Why can't she just live her life normally and have a good life, raise the kid, live in the house, make music, be happy?"

He adds, "Why does she always have to be in a struggle -- especially with people who care the most about her?"