When he and you both mature enough to understand that one person kissing another should not be considered a whore or anything bad. I have read that you are 13 and still learning about life and boys. This is not a bad thing at all. Perhaps your parent can help you out here?
Here's a suggestion for you: if it's possible, can you have a an important discussion with your mom about who and when to kiss a boy...and other important relationship issues ? What are her thoughts about this? After all, she is the one raising you and is responsible for you.