After 13 years, I went back to confession, and talked about a lot. In the weeks following, I realized that I had forgotten about many… some of them I’m pretty sure are mortal. I went back to confession and the Priest told me that I was being scrupulous… that all sins forgotten were absolved with the last confession. If I had any new ones, we could talk about those, and we did. I did not confess the forgotten ones, though. I’m feeling very guilty, but I know priests are holier than I. Do I really have the right to question him and am I really forgiven of those forgotten sins that have come to light?
I don’t know you personally so I have no way of knowing whether you are being overly scrupulous or not. Generally speaking, all sins that are forgotten by the penitent are indeed forgiven in the sacrament of confession. However, if someone remembers a mortal sin then he should confess it at the next reasonable opportunity.
If this is a priest that you have a relationship with and trust, then I would recommend you trust his advice. If this is a priest that you don’t know well and you feel that his advice is not applicable to your situation then I would recommend you confess your remembered mortal sins to another priest.