tl;dr: I moved in with my girlfriend and one of her friends without really thinking once I could move out of uni dorms, now I want to split the lease and I'm not sure how to bring it up

Hi shitlords. I met my current GF at college in my first year here. It's been two years since we got together. We're both 20. Our college has a rule that you must live in dorms for your first year. It really sucked, so I was excited to move into an apartment once that year was over. My girlfriend and her best friend asked me if I wanted to move in with them in an apartment for the next year, and I said yes because it sounded cool and I didn't know anyone else that I could be roommates with. We all moved into the same apartment and got on the same lease. After that year, my GF and I moved into a different apartment together (just the two of us) and are both on this lease.

As time has gone on, I have started to feel uneasy about this lease, because (god forbid) if something really changes in this relationship and either she really wants to break up with me or I really want to break up with her, I would still be contractually obligated to stay in or at least pay rent for this apartment. It's basically a contract that says "Do not break up", and that makes me feel very uneasy.

I want to split the lease so that just one of us is on the lease and the other just pays his/her share for the month to the person on the lease (the person still on the lease would be undertaking more financial risk, so I'd volunteer to do that since this isn't really about the money for me). I'm not sure how to bring up this topic phrasing it in terms of me wanting to have freedom and security, and not have my girlfriend think that I am preparing to break up with her. Can someone help me figure out how to do that?