Pregnant Evelyn Lozada -- I'm Having A Baby... And It's Not Chad 'Ochocinco' Johnson's

"Basketball Wives" star Evelyn Lozada has been keeping a big secret -- she's 6-months pregnant -- and TMZ has learned Chad Johnson is NOT the baby daddy.

Sources close to Lozada tell us ... she's been seeing a guy for almost a year now and the relationship has gotten serious.

We're told ... the pregnancy was planned -- it's not a case of the whoops! And until now only a small number of relatives were privy to the news.

Lozada famously divorced Chad Johnson in Sept. 2012 ... after an explosive domestic dispute ended their 2-month-old marriage.