What do you think?

What does it mean when a guy tells you he wants you to be more open? There’s this guy I’ve been talking to for a while (I was 17 when we met, now I’m 18 and he’s 22) tells me that he wants me to be more open with him. I have no clue what that means. I’ve been told by friends, and I know this too, that I’m very insecure. I think I’m ugly but others tell me I’m not and I think I’m not good enough for anyone and I think I’m too fat (I’m on a diet and losing weight (yay!)), plus I never say how I feel about anything cause I trust no one. I don’t know what it means to be ‘more open’ nor do I know how to be more open. I’m clueless as to what to do. I really like the guy, but I think he’s married and all this other stuff (he says he’s not and he wants me to stop thinking this way), but he always say he’s ‘busy’ for everything. I don’t think people can be that busy, and I’ve asked him this more than once, so I believe him. Anyways, what should I do?