Advice on how to explain the feeling that I've been waiting for too long

I am not looking to wed specifically but I've been lurking and feel like this community is closest to what I feel.

Me 35F and my bf 40M have been together for 10+ years. We have been in a long distance relationship for majority of our relationship. We met in person and started dating. We have lived together few times but have had to go back to distance due to life, work, family reasons.

We have talked a lot about the future and we are at the make it or break it point. He is now ready to sell his house and move to be with me. I am however avoiding that conversation like the plague as I am feeling so anxious about it.

I am now feeling like we waited for too long. I think for the past few years I've accepted that it is not going to happen. I'm alone in all the images in my head. I feel like this is similar feeling to those who were waiting for the proposal and when it happened, it didn't feel right.

He on the other hand is more certain than ever that he wants to do this now. I love him so much. I just have this rock on my heart. Some moments I'm so excited about our point future and the next moment I burst out crying.

What i need advice with is finding the right words to explain this to him. He hasn't done anything wrong, I should have talked to him sooner but I was fine-ish with status quo and all of this has been so gradual that I haven't really noticed it myself until now. I am still open to him moving in and us seeing how it goes but I feel like it would be wrong to let him sell his house and quit his job without telling him the full truth.