Am I a slut?

My friends are all calling me a slut because I started hanging out with the boys. I got into a conversation with 1 boy about dragon ball z and he introduced me to his friend's and ever since whenever in around my friends they laugh and say slut. I try to hang out with them but it makes me feel bad because they keep calling me a slut and saying how I'm getting railed by all of the boys and started rumors.... Am I a slut? Is it my fault for getting involved with the boys?