It is actually not hard to find a girl who is actually pretty and ready to commit. All you need to do is put your priorities right and go for the girl you actually feel you can go well with. Most of our choices and priorities while choosing spouses are usually conflicting and misplaced.
Being only 17, most of the people your age are probably not as likely to want to commit because they are so young. However, that doesn't mean that there is nobody your age that doesn't want to commit to one person. Be social and get to know lots of people. Join clubs at school. You already play sports so I'm sure you have a group of friends there. Have friends introduce you to their friends you don't know. Don't be to focused on finding someone. Just have fun with people and see if you are lucky enough to meet someone. If you don't give it time. As you get older you will be exposed to more girls that do want to commit. Try not to pass up on someone because they are not pretty enough. Of course you have to be attracted to someone physically but sometimes an average looking person can turn out to be a much better girlfriend than having one just because she is pretty. Someone that you get to know and like for their personality becomes pretty to you whether they are physically pretty or not. You will learn more about that as you get older.