Oh whoa wait a minute! You're the one working two jobs to pay for the boyfriend's school, while he's schnookering around with his "lab partner"! That's YOU! (I forget who's who when the pieces of story are in different threads.)
Ok, then what I just said goes twice as much. And I say dump the sonofabitch like, YESTERDAY.
Everything you are worried about and posted about before people's advice made you second-guess your gut feeling is true.
He "test-drove" the new model and decided to go ahead and trade the old one in. He's not man enough to break up with you because it would make him the "bad guy". You don't want him to be the "bad guy" but at the same time you don't want to be where you are.