Girls I need your advice.

My now fiance wants us to take a trip away and go on a little holiday with me and his family. That bit I don't mind. When we were just dating, we went out for a family outing and he was looking at another female that he knew and started talking to her. She started the conversation first, she was looking at us holding hands and looked like she couldn't wait to talk to him. It made me feel so little, I stopped holding hands and walked off with my family. He told me he is sorry, then we walked back passed and he was still looking at her! That was months ago. I think I'm still so hurt by it and that's the reason I don't want to go. I don't want to feel so little and shit again. I told him that I'm not keen on going, if we do I want our own room away from his family. I don't want to bring it up to him because I know he will say "that was ages ago, I haven't done anything to you since" I think im still so hurt by it. Any advice please!!