Low Confidence

I have a low self esteem and low confidence.  I recently started seeing this guy, who's very confident, and outspoken. He has pointed out to me how reserved and quiet I can be and when he does that it makes me feel awful. That's just the way I am. Idk if he's saying it like if it's a flaw or not, but it makes me feel awful. It takes me forever to be able to open up to someone new, and I feel like I haven't been able to be open with him yet. I'm very closed off. What can I do to be more confident and outspoken? I don't want to be this way anymore but I really can't see a way out of this. I feel trapped, imprisoned, and I just don't see myself ever being confident and outspoken and open with anyone. I really like this guy and I'm afraid I'll lose him soon. I'm a very good girl, quite a catch actually.