How do I make friends at my school?

I have been at my school for five months and I have no friends. I'm actually a very friendly person, and it'a easy for me to make friends, but no one in my cl in accepting. There are about 15 people in my cl. One group of girls are the 'popular girls' who don't take anyone new, the other group is the 'wannebes', who want to be popular but aren't. There is another girl, Brittany, who is always alone. I tried being friends with her, but she's rude and VERY disgusting. I'm talking about the kind of person who burps in your face. And she rude, like I said. The boys are all in one group, and they don't respect girls. I've got one or two cl friends, the kind where the friendship ends in cl, and sometimes we say hi to each other in the corridors. Apart from that, I have no friends. 5 more months of school to go. How do I make new friends?