I know exactly what you are going through. I'm the same way. Met a great guy and I kept waiting for him to change or walk away. Honestly, I still wait for that to happen. It took me a very long time to open up to him, but I have been able to after 16 months. Somewhat.
Before then, I would try to talk and you're right, the words will just NOT come out. I started saying things like, "I enjoy talking to you". Later, it became something like "It's not that I don't want to tell you things, but I just can't yet. It has nothing to do with you, but with my past experiences, I'm unable to right now". Granted, it took me at least 8 months to even say that much.
With time and his patience, I have shared a lot with him. I still haven't said the words "I like you" nor can I usually admit things such as missing him. He understands and has learned that when I deflect a certain way, it isn't that I don't care, but that I can't say how I feel. He never guilts me or pressures me to give more than I can. He accepts that it is easier for me to show affection by thoughtful gifts and that my reaching out to him when I am upset shows that I do trust him. I'm very lucky.
I think if you tell him that it's hard for you to open up, but you're trying...he'll be like the guy I'm talking to. There are some really good ones out there. Looks like you may have found one yourself!
[This message edited by BeingNaive at 4:36 PM, Wednesday, May 11th]