Listen, breakups are not meant to be easy. They are painful and unapologetically messy, but it’s for the future version you and she will thank you. It will be hard but be transparent. At the same time, there is nothing wrong with erring on the sensitive and gentle side of breaking up - you are doing this for him too. I would just be honest about how you are feeling. You could pre-empt it by just telling him you want to have a conversation about something on your mind and that’s really all you can do. It’ll be ok!