How can I stop this teasing?

I’m 16 years old and I recently noticed that a lot of girls at my school have taken an interest in teasing me. They’ll just laugh and talk about me loudly when I’m around, one of them even called me ugly! I’ve counted and so far there have been about 15 girls who have teased me ( particularly the popular ones).My friend and I were walking down the hall at lunch today and a group of them even followed us to laugh! I don’t know what the problem is, I dress normal and act normal (lol, at school at least, haha) and haven’t given anyone a reason to dislike me.I mind my own business, keep to myself and am generally nice to everybody. Up until this point, I’ve been ignoring it, but enough is enough, I’m struggling with depression right now and I don’t need this shit on my plate too. How can I put an end to this without causing a huge uproar. I’m placid by nature, and I really don’t wanna start a fight, but it seems like that’s what they want. Why are they picking on me and what’s the best thing to do? I appreciate any answers, thanks.