why would you say you wont be with anybody else if you are not exclusive or in a commited relationship?

it feels like you wanted to be exclusive and before that this last encounter happenned.

if you feel being exclusive with your gf is not natural or something you really feel genuinely about, be open about what happenned to your girlfriend and let her decide.

its not a very good situation to be in but be honest with yourself, do what is right for you.