How to stop pimples on my head/in my hair?

I don't know why, but I am constantly getting pimples in my hair. I was getting them worse whenever my hair was longer, but now it is really short and I am still getting them, but not as worse. I was wondering what I could do to stop them. I only get them mainly on the sides and back of my head. (I am a guy, by the way).How to stop pimples on my head/in my hair?
It may be because you don't put enough soap on those areas when you are washing your hair. Just remember to lather, rinse, and repeat on all parts of your hair the next time you take a shower. It also may be because you don't wash your hair enough. Some people may need to wash their hair everyday and some every other day. It depends on how oily your hair is. It may also be the kind of shampoo you use. It might not be the right one for you.