Help quick please - girlfriend dilemma!?

I used to have the same problem with my boyfriend, and in the end I told him how I felt. It seemed to have worked, but we still broke up because we switched schools. Point is you should talk to her about how you feel. Girls sometimes feel like our boyfriends don't talk to us about what's on their mind, or about how they feel, enough. If that doesn't work then have you considered taking a break and letting her figure out what she wants? How does Chloe act when she doesn't have Sam around? In short you should just talk to her about how you're feeling, and tell her to think of Sam's girlfriend and how she must feel with him flirting around with other girls. You could also just talk to Sam's girlfriend and see if she has any advice for you, because I know that if I were her I would've broken up with him already. If you have any additional questions, or need more advice feel free to message me. Hope this helps! Good luck!