'Teen Mom' Star Ryan Edwards Arrested Day After Wife's Pregnancy News

"Teen Mom" star Ryan Edwards really killed the mood -- one day after he and his wife announced they're expecting their first child, he went and got his ass arrested.

Law enforcement sources tell us ... the 30-year-old was busted Tuesday at his house in Tennessee when cops executed a warrant for violating probation. We're told he posted bail Wednesday morning. He's already on probation for a previous heroin case.

Ryan reportedly had a $10k-a-week heroin addiction before going to rehab -- and MTV cameras captured him slurring his speech and falling asleep at the wheel on his way to his wedding last year.