How to walk straight?

Some people have told me that I walk like a girl. In fact, I had a teacher bully me for my way of walking. I think I walk this way because I come from a home where there are no boys, so I may have subconciously imitated them as I grew up. I try to force my hips into staying still, but it's hard to me, and I realized it's even harder when I'm tired. Can anyone tell me how to "walk like a boy"? Help/Tips?