irrational fear or real problem

so my current BF is the only person I've ever had sex with, we've been having sex for over a year. (together 1 1/2 years) I'm genuinely terrified that if we break up I might turn into a huge slut... we have sex as much as possible. We're the same age but he's a junior and I'm a senior in high school. I'm not worried about college changing me or taking me away from him, I'll be living at home and going to community college for the first two years, but how am I suppose to keep "her" happy if we do break up?