Breaking up

So, my boyfriend of almost 4 years just confided in me that he's not happy with our relationship anymore and he doesn't know why. Now I'm not exactly 100% happy either and I'm positive that we'll break up at some point in the near future. I'm surprisingly okay with that, I know it'll be hard but it's mutual... My problem is we live together and our lease is up in September ( we paid first and last so technically I could leave in August) but I can't pay for the apartment myself and I don't know what I'll do when our lease is up... Please, if you've got any advice, help me out...