it comes in time dont worry about it, I went to a single sex school and can relate to your probs. Generally we tend to dissasociate with the opposite sex at about 8-10 or so and then reconnect later in our teens. If you arent around girls at this time you kinda lose out on building those skills. Its not a prob though, I fell in with a new crowd at about 16 and by the time I hit Uni I had all the skills required, just observe those around you. Learn how to pay compliments, listen, and how to make it clear that you are interested in them and not just as a friend!
You might want to think about the message your appearence sends out - sure to you its a freedom of expression but it will put plenty of people off. As you get older you'll realise that making a statement of individuality isnt all that important as your confidence in your self grows. Its your choice of course, but dont deny the consequences of your choice and ask yourself if its really worth it!
GL.