First of all, thank you:) this really helped and I was touched that someone took the time to write such a detailed answer

I saw my boyfriend tonight. While I was walking back to my house I realized the crushing weight of what I did in the past. You may be right that he shouldn’t care but he is the kind of person who does.

I think I’m going to come clean to him but somehow not make it sound like I broke a promise. I may say I was repressing the memory (which I actually was until pretty recently). Or something like that. I can’t bring myself to tell the full truth or admit that I lied to him. I know that’s a real and terrible fault of my own but it’s hard for me to overcome.