Chad Johnson's Baby Mama -- Don't Make Me Pay ... For His Stupid Mistakes!

Just because Chad Johnson's finances are in the toilet doesn't mean his baby mama should have to suffer from a tighter wallet ... at least according to her.

Andrea Pearson filed legal docs in FL court -- firing back a Chad's request to reduce his $5,240 / month child support bill. Chad claims he can't afford it anymore, after getting fired from the NFL and losing his lucrative endorsement deals ... circumstances he says that were out of his control.

But Andrea argues in docs ... she shouldn't be punished for Chad's screw ups, clearly stating that his money problems ARE his fault, explaining, "he sabotaged his own earning ability through his conduct and criminal behavior."

Translation: The head-butting, domestic violence arrest (the catalyst for his $$$ woes) was Chad's doing ... and Andrea doesn't want her support cash to be collateral damage.