18 years old, male, 2 year relationship. Basically, I have to tell my girlfriend EVERYTHING in my mind and that I have done in order to have a "real" relationship and connect with her. If literally 100% of the truth isn't out on the table, everything from the dirty sexual details of the past to my thoughts and sexual fantasies, the relationship will never be the same. That is my thought process, and every time something comes up, I confess. This has been hurting her, and it is selfish of me because it only brings temporary relief until I find something else; the truth is never 100% out there.
Recently, however, I did mess up for real, and I cheated. I made out while drunk with a girl, and I ended up telling my girlfriend this, rightfully so, as I felt horrible. We both went through pain, and she managed to forgive me. However, when I told her, I made the details less intense out of fear of her losing me. First I said it was only a kiss, then later told her it was a make out. This hurt her (me lying partially), but she managed to forgive me. This was months ago.
Today, out of nowhere, a detail that I made less intense reemerged in my head and has not left me- again, this time MONTHS later after everything has been honest and strong after rebuilding. I told her before that the girl "attacked" me, threw herself on me, then I accepted her and we made out together. In reality, it was more mutual, as I came onto her just as much as she came onto me. I feel the strongest urge to confess this, as in my head, she must know every detail. However, I know that if I tell her this, especially months later, she will leave me completely and doubt everything I have ever said, as I would once again be adding more to the story. The problem is, I know that me telling her would bring me relief, and bring her pain. Eventually, I will find even more detail I have to tell her, ie, whether i enjoyed it or not, how long, etc. My girlfriend already knows the big picture facts: I cheated, I made out with another girl, I kept it going. We got over that, and that's what matters. Bringing this up would destroy us, and even if she forgave me, I know I would have to find more details down the road. But I feel like if I don't tell her EVERYTHING, we will never work. Everyone has secrets though that others don't need to know; for example, she left me for a month and slept with her ex, but claims she forgets how many times and that she didn't like it- she probably knows how many times and did enjoy it, but that isn't a detail I need to know.
Is this something I must confess? Or is it something I am doing selfishly just to relieve myself? Will it be insignificant in the long run if I learn to control my compulsions? I need reassurance in some form, if this really is OCD, and just another detail that I want to confess in my neverending journey for a "perfect," 100% honest relationship. Any advice, feedback, assurance, personal stories would help. Thanks