The desire to wear women’s undergarments is not an unusual fetish. Generally, most therapists would not find it to be problematic unless someone was being harmed. The problem in this situation is twofold: you are unable to stop yourself from wearing your stepdaughter’s panties and your wife has threatened you with divorce.
I am interested in what you said about your stepdaughter knowing that you are wearing her panties and her being okay with it. I am wondering how you know she is okay with it. Did she tell you that? Did she catch you in the act and not say anything to you? Perhaps, she is not okay with your behavior but she may not know what to do about it. From her perspective, please understand that she may find your behavior to be unacceptable but she doesn’t know how to handle the situation. It sends very mixed messages. She may not understand that you are wearing her panties because you feel a strong desire to wear women’s undergarments. Rather, she may believe that you are wearing her panties because they have some connection to her. That might be very traumatic and confusing to her. For that reason, wearing her panties might actually be psychologically damaging to her. If so, it has to stop. If you want to wear panties then you should purchase them and not wear your stepdaughter’s.
I want to reiterate that the desire to wear panties is not necessarily a bad thing. As I mentioned above, it is not an uncommon fetish. The problem is that you are taking panties from your stepdaughter and she may be getting the wrong idea about your behavior. You can’t allow that to continue.
The other issue is that you are hiding your behavior from your wife. It is never a good idea to lie to your spouse. Honesty is the foundation of every relationship and when it is broken it may be difficult to repair. She may be okay with the fact that you find it erotic to wear women’s panties but she may be upset and angry to learn that you are taking them from her daughter.
I am assuming that you are hiding your behavior from your wife because you fear her reaction. My suggestion in this situation is that you either tell your wife or consider seeing a therapist who can guide you about how to deal with this situation. There is probably much that you feel that you have not written in this letter. It would be helpful if you had someone who could advise you about how to deal with the whole issue. Specifically, the aspect of sexual arousal from wearing women’s clothing and how to deal with this situation in your marriage.
As I mentioned earlier I would also advise you to stop taking your stepdaughter’s panties. Your behavior is inappropriate and must stop.
You may want to consider seeing a sex therapist. Therapists who do not receive specific training in sex therapy may be helpful but a sex therapist focuses on understanding fetishes and other related sex issues. Here’s a link to a website where you can search for a therapist in your community. Thanks for your question.