Ex-NFL star Warren Sapp is desperate to lower his child support payments … even though he struck a deal with one of his baby mamas to NEVER change the amount — of course, that was before he went broke.

He has been paying baby mama Angela Sanders a total of $2,500 a month, but recently filed documents in a Florida court to have that number modified, as Sapp is facing some serious financial struggles through bankruptcy.   The main issue here is that the previous agreement he made with Ms. Sanders in 2001 stated that neither party could “seek modification” for the child support payments based off of income alterations.

Problem is, back in 2001 — when Sapp was a Tampa Bay Buccaneers cash-making superstar — he and Sanders added a clause to their child support agreement that said … neither party could “seek modification” based on changes in income.

Presumably, Sapp was trying to protect his millions.

Sanders tells TMZ she’s “frustrated” by Sapp’s request … because she was fine sticking to the $2,500 a month while his pockets were getting fatter — so it’s unfair for him to lower it now.

According to the docs, Sapp is also trying to modify child-support payments for his 4 other baby mamas.

A judge has yet to rule.

Get it together Warren!!