Jenelle Evans and her on-again fiance Gary Head are both behind bars, a source tells Us Weekly -- Head for domestic violence, and Evans for drug possession. reports the pair were partying with pals when they got into a heated argument. During their spat, Head "hit her numerous times."

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Evans has also been arrested, for possession of an illegal substance. If charged with assault, Head, a Marine, faces serious jail-time, and will most likely be dishonorably discharged from military service.

In April, the mom to Jace, 2, accused her then ex-boyfriend of getting physical during an altercation, though she didn't press charges at the time. The MTV star tweeted that she did "call the cops," but "told them I didn't want to press charges to jeopardize his career."

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By early May, the pair had reconciled -- and on May 16, Head popped the question to Evans with a diamond sparkler.

Tweeted Evans, "I'm the luckiest girl in the world to have Gary Head in my life."

This article originally appeared on Teen Mom 2's Jenelle Evans, Fiance Gary Head in Jail