My boyfriend and i are signing a lease, we also have a co-signer, if we break up can i get off the lease?

No...you cannot get off the lease and will still be legally liable for payments until the end of the first year when the lease goes month-to-month. You should have a WRITTEN agreement between you and your boyfriend as to what happens if you break up. If the agreement is not written, it is no agreement at all..verbal real estate agreements are not valid in court.