I'm a female with all male friends?

I’m a 20 year old female, and as long as I can remember, I have always had almost all male friends. I’m not a tomboy, if anything I’m on the girly side, I grew up with two older sisters. I literally have maybe two girlfriends, and a dozen or so male friends. These friendships are all strictly platonic. I have a boyfriend, and the fact that I have so many male friends bothers him a little, I can understand why. I’ve read that women in situations like this suffer from low self-esteem, but I really don’t. I just feel my male friends are more laid back, less judgmental, and less dramatic. Is this unusual? What are some possible reasons for my gravitation towards guys vrs girls for friendship?