There has been quite a few posts about this kind of thing, OP. There will be different advice, ranging from loving your waifu and not daring to think about any other, to going with what makes you the most happiest (which sounds like what that new girl is making you feel). My advice? Give it some time. If it hurts you so much that you can't be patient, then I suggest giving yourself some distance between both of the girls-- although, from what you're saying, it sounds like you're just infatuated for a short while, a phase alot of us here go through.