Lizzy, are you sure it's you? Do you feel out of whack or particularly emotional (the reason I ask is because pre-OCP I suffered from horrendous PMS and I always knew when I was 'on' because I just didn't feel like myself at all). Do you agree with what your partner is saying or do you think there are some underlying tensions (from either party) that are subconsciously keeping one of you from wanting to commit?

Sorry, not trying to psychoanalyse, but I think it's important you work out what the dynamic actually is. If you think what he says is true and you really are hormonal, I would suggest seeing a naturopath or a Traditional Chinese Medicine practitioner, they have some awesome herbs that sort that sort of thing out (speaking from experience)! Also, try to focus on how much you love your partner and enjoying each other's company, the rest will come naturally...
:-)