How can I legally break my lease?

I'm leaving on may first to go study abroad. I've been living in my apartment (in Manitoba) for almost 3 years, my lease renewal is up on July 1. I gave them 2 months notice (I thought that after 1 year all I had to do was give 2 months notice), but they told me I had to sublet or pay up. I'm beginning to worry as the apartment is not sublet yet and I can't stay in Canada. Is there anyway that I can break this lease - I can't afford to pay rent for the next 2 months here.