I'm not offended in the least.
What this boils down to, it seems to me, is whether you're going to throw away a relationship you've built over the last 11 years for the sake of something that happened 5 years before you met your partner. In that time, you've presumably got to know him pretty well. Is he a good man? If the answer is "yes", then the best course of action it seems to me, difficult though it is, would be to work with him and decide together what's the best way to handle this very difficult situation. But only you can answer the question as to whether your relationship is worth saving.
I wish you the very best of luck, whatever the outcome of the situation. It must be a very difficult time for both of you.