Hihi :) Firstly, I wanted to apologize for you not really getting that much help in your topic, but I'm glad you came to the eHelp system instead. Hopefully we can help a bit, and if not, feel free to message me afterwords if you need clarification/want to keep talking. :) But onwards!:
You gave him the benefit of the doubt and tried to give him the chance that you felt he deserved. Perhaps he was going to open up eventually, perhaps not, you still took the risk of going out with him and seeing if he'd actually change. The fact is, that sometimes people are going to remain quiet. Some people are so overwhelmingly self-conscious and unable to break out of their boxes, that they stay to themselves and go throughout life rarely bothering people here and there. Whether it be from things in his past that are bothering him and disallowing him to move on, or him being uncomfortable with the situation as a whole, who truly knows besides him. Have you tried taking in his situation as a whole? (Meaning: His life, stress, perhaps you're his first girlfriend, etc. Anything that could impact how he is.) Have you tried talking to him about this as a whole?
Chances are he's not even aware that there is a problem. Think about it, he's always been shy and kept to himself. He never went along with anything, and he never really spoke out. Right now, what he's doing, is normal to him and his lifestyle. So it's going to be hard for him to notice that there is a problem, especially when you haven't (if you haven't) tried to full on talk to him about it. Show him how much this is upsetting you, show him how much he means to you, and show him how much you love him. Sometimes we just need a little boost in our lives to show us there is something wrong. :) He still has the capability of opening up and changing, but these things take a bit of time.
Make him feel comfortable. Do things and talk about things that interest him. Don't move too fast within the relationship, and don't do anything that might make him feel uncomfortable around you. He definitely likes you if he's going out with you, right? He just needs a little time to change. The relationship has the capability to work out. Talk to him, talk to him, talk to him. I know it sounds like a generic answer, but just talk to him about anything and everything. About your life, his life, what's bothering you, him, why he's acting like this, etc. Anything. Just put forth a little more effort than you have been, and try to get him to do the same.
There is a point where you have to draw the line, but from the sounds of it, you're no where near it yet. Go out on dates here and there, express your love towards him, be romantic, and just allow him to progress as time goes on. You can't force him to change, you can only sit back and hope for the best. :) My best recommendation to you would be to stay calm and be yourself. Definitely if an issue arises. Never point out faults he has, unless it's trying to get him to talk more. Be yourself, and be prepared for anything. Who knows, one day he might just start talking. I wish you luck, and if you ever want to talk, feel free to message me. :)
~Wayne