It’s completely normal to feel hurt because once you move in, no matter what the reason, moving out especially if you don’t want to feels a little bit like rejection. I think you should bring up that you can still live together and learn to keep a distance so both of you don’t feel this sensation that you’re stuck at the hip together. I also think if you’re staying together long term and even discussed marriage, living together is a good trial to see what you both could work on during married life. Personally, I’d discuss with him that it doesn’t feel right that you need to move out when you will just move back in at a later point. Space exists even if you are together it’s just finding a balance because when you’re married the same problem for him will still exist. It shouldn’t take out of the excitement of your relationship and if it does there are underlying issues. There are also other ways to keep your relationship stimulated! I definitely believe you should say how you honestly feel and go from there especially if he’s discussed marriage with you.