Please note: my question concerns certain details that are, shall we say, personal and difficult to talk about. So, be forewarned before reading on.
I have struggled for a long time with the sin of self-abuse. Recently, I went to confession and naturally named this sin as my most serious, and then went on to my other sins. However, I did not mention that there had been several occasions on which I had done it in bed, in the middle of the night, while my roommate was sleeping in the same room as me. Obviously, my concern is that the possibility of scandal (while admittedly small, since as I mentioned he was sleeping at the time) made the sin more severe, but I did not mention it because...well, it seemed like a weird thing to say. I've pretty much accepted the fact that I was wrong not to mention this caveat, but I'm wondering if it was enough to invalidate the sacrament. On the one hand, the "base sin," if you will, was masturbation, and I confessed that; on the other, I know that scandal is also a sin. But then again, I was reasonably certain that there had been no scandal, so I felt justified at the time in not adding that caveat. I know there are a lot of issues here, particularly about the fact that trying to avoid embarrassment is not the right attitude with which to view the Sacrament of Penance, but the one I am specifically interested in here is that of validity.
Do I need to reconfess? If so, what should I tell the priest?