What should I do with this girl?

I'll keep the details short and sweet : I like girl, girl likes me, we hang out in a Platonic sense. I find out she has a boyfriend. They brake up and a month or so later, we start to pick up and seems like us starting a relationship is inevitable. We disappear from each other due to exams, come back to find out she has returned to her boyfriend. In September or so, they brake up because he cheated on her and here we are today seemingly picking up where we left off before the exams.





I want to ask her this to make sure that I am not just going to get burned again.





';I really like you, and the last time this came up you ended up going back to your ex, which was fine. I respect that decision, but right now I just want to know, are things going to be the same as last time? I like you, but I don't want to be used';





Is this fair question to ask? How would you ask it if you could?What should I do with this girl?
Be a little nicer with it. Don't put her down for making a mistake.