Dear Peaches:
Having the past experience of a person who “would always belittle me and criticize everything I would do”, no wonder you are afraid to share, to open up, to peel off the layers of the onion, figuratively.
You wrote, “I really want to… but I don’t even know where to start?” – how about this very thing, your fear of sharing, of opening up and getting criticism in return. You can ask him if he would like you to open up and share more about your feelings and thoughts and if he can listen to it without criticizing you.
Share that and listen to his response. I would be interested to learn if and how he responds.
anita