Not a gals gal?

For as long as I can remember I've struggled making girl friends. I have a few close girl friends that I've been friends with since high school but I have yet to make a friend as an adult. I'll be honest, I'm introvert, don't get out much, and I have a few hobbies/things I'm passionate about. I've come to the conclusion that maybe I'm just a boring person? Lol Or maybe I'm just picky about who I let into my life? When I'm talking to a girl (depending on what she is like) I just kinda freeze up and can't open up to her. My best friend tells me that I was a hard egg to crack. I don't know why I have such a hard time letting girls in. They're just intimidating to me sometimes. On the other hand, my husband has NO problem making friends. He has more guy friends than I have girl friends. Sometimes I think because I'm an only child I'm this way but who knows...