boyfriend driving me nuts

I. Am. Going. To. Lose. It. 
My boyfriend and I have been together for 3 years and we moved really fast. A month after dating we moved to another province (in Canada) anyway. Things were great! He hasn't been the best with money, it always seems to be pay check to pay check and I since moving back to our home town got a high paying job and make more than he does by a lot. I don't know if it's an ego killer or what but he's been acting so much more immature. I just bought a house for us to live in. His credit isn't the best so technically the house is only in my name. But WE will be together in it as a couple for I hope forever. ANYWAY he's been just acting so immature!! And it's driving me insane. He owes me money from a vacation we went on ($1600) but hasn't paid any of it back and it's been 5 months. He sucks at having grown up conversations he just gets defensive. Ugh. 
Update: the $1600 was a trip to Mexico that  we decided we would pay our own ways for a wedding. Yes, I make more than him. But he made the decision to pay his way.