I have been with my partner for three years, and a month ago she cheated on me. We discussed the matter and from that I discovered that this guy she cheated with is well endowed, lasted longer than me and has a huge sex drive. She now wants us to fix things, but I am uncomfortable knowing all of this. I am afraid that I will not satisfy her and she may end up going back to this person and that I’ll be hurt. What can I possibly do to overcome all of this? Don’t believe your partner’s description of the other guy. It sounds spiteful. Is there a reason why she would try to hurt you? Is she angry or resentful of you for some reason? It’s time for a calm talk to try to understand each other far better and to have a chance to express your true feelings without resorting to blaming or name-calling. Tell her honestly that you feel uncomfortable and afraid and say: “Please help me to understand your feelings too.” After a breach of trust it takes time to repair a damaged relationship and the hazy spectre of a rival’s dimensions is really the least of your worries. Pamela Stephenson Connolly is a US-based psychotherapist who specialises in treating sexual disorders. If you would like advice from Pamela on sexual matters, send us a brief description of your concerns to private.lives@theguardian.com (please don’t send attachments). Each week, Pamela chooses one problem to answer, which will be published online. She regrets that she cannot enter into personal correspondence. Submissions are subject to our terms and conditions: see gu.com/letters-terms. Comments on this piece are premoderated to ensure discussion remains on topics raised by the writer. Please be aware there may be a short delay in comments appearing on the site.