Selena Gomez Wears Justin Bieber's Hockey Jersey

Selena Gomez and Justin Bieber sealed the deal -- 'cause nothing screams we're back together like a chick happily slipping into her guy's sweaty jersey!

Selena was beaming on the ice as she watched Justin's hockey scrimmage Wednesday night in Los Angeles. While they haven't made any official announcement ... c'mon ... no woman's sitting through a guy's glorified practice, unless she's banging him.

Right afterward, the couple left the rink together -- Justin still sweatin' and Selena sporting a hoodie and the jersey.

They're in full-time inseparable mode now. Earlier in the day, they took a bike ride together too. Not to mention their day-into-night date on Sunday.

Next she'll be wearing his varsity jacket. Oh wait, Bieber probably didn't get one of those. Too busy making a gazillion bucks and stuff.