Adrian Peterson -- Wife's Preggo ... With His 8th Kid!!!

There's NO slowing down Adrian Peterson -- especially when it comes to reproduction -- 'cause his wife announced she's 5 months preggo ... which brings his count to EIGHT ... depending on who you believe.

Peterson's wife, Ashley, just broke the baby news to ESPN ... telling the network she's pregnant with Adrian's 6th child.

But back in 2013, Peterson's baby mama #2 Erica Syion told TMZ she knew there were 7 OTHER KIDS.

Of course, one of Peterson's children -- a son that he had never met -- was killed in 2013.

Peterson got married to Ashley in 2014. They already have one child together.