'This S**t Is Tearing Me Up'

An extremely emotional Arian Foster EXPLODED on a reporter in Houston moments ago -- telling the guy the legal war with his pregnant baby mama is "tearing me up."

The reporter, who works for FOX 26 in Houston had gone to Arian's home to get a comment -- standard operating procedure in the news world -- and that's when Arian went off.

The Houston Texans running back stood in his driveway and made it clear, he's not ready to open up about the situation yet ... yelling, "I'll talk to y'all when I feel it's right."

TMZ Sports broke the story ... Arian -- who's married with children -- is being sued by a college student who says the NFL star pressured her to get an abortion and refuses to help out financially with the pregnancy.