Am I intimidating? Or too grown up? Or what's the problem?!?

Seems like every time I get close to a guy, and become really good friends they end up getting a girlfriend and then stop talking to me. I really would like to know what's going on. The only guys who have ever been interested in a relationship with me have been real needy guys or guys who have a lot of issues that they need to get figured out.

Here's a little bit about me:

I'm a the oldest of 10 children, I love them all very much, and love spending time with them. I also love spending time with any child, I've been told that I have a very nurturing character. I love to cook, not particularly for myself, but I really love to cook for other people. I am not the type of person who likes to go out and party, I don't drink and have a very hard time doing anything out of the ordinary and generally don't do crazy things. I absolutely love people, love listening to them, especially those who just need someone to talk to and vent to. Could this be intimidating to guys? Or what else could be the problem? I'm just really confused right now.