Somethings telling me to pull away but I can't

For context, I 18F have been talking to 18M, we started off as friends and we both had developed feelings for each other pretty quick, I'm not good with relationships due to past trauma with them and that has caused me to not want to rush into anything just yet. We have had occasional times where he wanted to just call it all off, and everytime we had worked it out in the end. I do really care for him as a person but I just feel like something inside of me is terrified of this. I have bad attachment issues and I've not had a good outlook on relationships. I don't question this person's love for me at all. Yesterday we had shared something pretty personal and although I felt like I wanted it at the time, waking up I feel different about it. I don't entirely regret it, but I just feel that same agonising fear. It's making me want to pull away and just tell him to find someone else that can love him the way he deserves, even if the idea of him with someone else kinda hurts. I feel like a coward for wanting to run from this but I just don't know what to do, I feel lost.