My DH and I have survived from an affair (of about a year or two *wow* I can't believe I'm forgetting how long it was
plus other cheating events which led up to and included the longer affair. This was disclosed about 5 years ago (which I also had to calculate). We've been together for 18 years now.
The only thing I can really say is that it IS possible to heal the trust but it takes a lot of Time, openness and vulnerability from both of you. For me, I needed total transparency and a refocussing/rehauling on our marriage and family and my DH was willing to do so happily. This lasted about two years post affair disclosure. The other thing that I really had to evaluate was what *I* wanted out of the relationship regardless of any other possible people. The cheating ultimately revealed to my DH (and to me) that he would like an ethical non-mono/open to poly relationship and that while he was patient, and wouldn't consider leaving me, he felt this is what he ultimately needed for his own happiness.
During the refocusing time we spent a lot of time discussing and sharing what we both wanted out of our relationship. We discovered we have way more relationship/lifing overlaps than not. Plus, we love each other immensely- we just have some rough edges. With time and seeing how our relationship transformed for the better, and that we shared many if not most of the same goals, trust and confidence came much more easily.
For you, you might want to ask him about your needs for intimacy and BDSM. Since you brought them up in your post I imagine these are two very important things to you, and the deception around them while your needs were not being met add to your pain. It would be good to know now if these things are important and meaningful to your partner as well in your relationship and how he intends to make sure these aspects of your relationship will remain nourished and fed by BOTH of you. As well as any other things you feel are important or meaningful. All LTRs ebb and flow but if you both develop ways that you can re-center back to the agreed upon fundamentals w/o getting in a negative loop it goes a long way to smooth and soothe the relationship weather.
If you come to know that you are "on the same team" so to speak within the relationship you will begin to feel more secure and trusting- even in difficult times. Unfortunately, after an affair like this, it frequently doesn't feel like our partners are on the same team for our relationships. In fact, it feels like the opposite due to all of the lying and deception and emotional drama that backlashes from the affairs. Not just your hurt- but their hurt as well reverberating through the relationship post facto. It can be very confusing.
I believe I understand this feeling. I was a wreck after my DH came clean to me mostly from the abandonment I felt from him checking out of our relationship over the previous years and my recent belief that I was not respected/supported at all by him. He was a wreck as well. I needed constant reassurance and loving actions in the beginning to forge a new pattern of believing his words and believing he was really committed to our relationship and our family again.
I gave it time, so did DH. We are much better for it now. We love each other completely and I believe we have a strong foundation. Stronger than we ever had in the past. It's not always easy. We still have some moments when we trigger each other and then have to dig ourselves out of it but we recognize the pattern and we are both working on it. It is not as distressing anymore but I (we) would like to be able to move past it or at least improve it.
I finally started reading a book (after a classic trigger snafu) that I bought after the last time we had a trigger-fest emotional breakdown. It's called "How to Improve Your Marriage Without Talking About It," by Patricia Love and Steven Stosny. It is pretty heteronormative and geared towards a general monogamous audience but the fear/shame cycle is what I experience in my relationship and I have found it very helpful in better understanding BOTH of our POVs. I believe it is primarily about rediscovering compassion for and with each other and believing we both primarily want the same thing- connection. Many of the points they make we had already started to do on our own in our relationship. I am still finishing it but it has a very strong start that I am happy to have found. Maybe it can help you as well.
I read this article which ultimately led me to buying the book:
If it resonates at all with you give the book a shot. It was eerily similar to our relationship conflicts.
P.S. I think you were very brave and open to try and work things out with your partner's OSO. Especially right away. I am glad that your were able to experience some healing with her. That is really great and will be helpful to you in the future I believe. However, I think having emotional breakdowns every 3-4 days is not a good place to start making huge relationship changes from. That doesn't give you enough time to reach center, process, and start fresh and stable within your relationship. That can be more damaging in the long run because of the pattern up upset and drama that frequently follows.
We realized that a slower pace was much better for us to maintain more stability and happiness in our life and our family. If anything, I hope you are able to look out for your own emotional needs as you both move forward. Small challenges are good, IMO. Frequent large ones can have a tendency to backfire in our faces if we are not compassionate towards our own needs.
As for your obsessive thoughts happening right now- If your partner, from now on treats you with respect and good faith, the obsessive thoughts and distrust will fade with time because they will be replaced with new positive memories. If he does remain consistent and several months later you still feel frozen with obsessive thoughts perhaps focusing on yourself and your own individual happiness is in order. If he doesn't treat you consistently well, there will be good reason they don't fade. It took me about two years to settle my anxiety and obsessive thoughts so that weeks or months could go by without them bothering me significantly.