How can I stop this? The other girls at school have started to call me a slut and this affects how boys see me and they expect more from me, inappropriate things.

You continue being your awesome self.

Grant friendship and the dates you want with the people that want to befriend, date, and respect you back.

Block and ghost the girls and boys that disrespect you.

Be the bad ass that you already are, admire your ability to enforce your boundaries, and recruit more respectful and better people to be on Team You.

The others get no play.

If the abusers continue their shitty bullying, get caregivers, parents, teachers, counselors, and possibly even law enforcement involved to shut that nonsense down with a quickness.