I have cheated on every girlfriend I have ever had. I have a new one who I luve but I kissed another girl. I really think this will be the last time.

Should I try, Or break up with her to avoid hurting her/ I think she oucl be the one?

Instead of cheating on girlfriends and dooming your relationships to failure (which may be why you're doing this because you're afraid of relationship) why not try dating and not being exclusive - BE UPFRONT with all parties and find like-minded individuals. Be mature --
Have you thought about open relationships?

Just stop cheating and continue the relationship peacefully, if you don't care for the relationship to the point where you feel the need to cheat, then YOU are setting yourself up for failure, no one else.