Best thing to do now is buy a cheap disc, maybe even second-hand one since you bought the online pass.
I can't level up pass level 15
It really would have helped if you said this in your OP, cause now I know the problem.
You're on the Free to Play version on the MP, which doesn't need an Online Pass to play and only goes up to level 15. If you want to level up more, you need to purchase the no level cap unlock (which I DO NOT recommend) or buy the Game of the Year version of the game with a lot of DLC on it (please do this instead).