So, everything in our/my culture is telling me that it is wrong to ask for what I want.
Are you saying that you are also experiencing a crisis of faith?
It's possible. Sometimes that is a part of maturing/getting older.
We begin with what our families/society teach us. Eventually there comes a time where we accept what's going on from the external authority. "I do this because my parents says so... I do this because church says so... I do this because the laws say so...."
Eventually there comes a time where YOU become the internal authority. "I do this because I say so." You have actually reflected on the values given to you by your family/society and made an evaluation of them. You don't accept them on "automatic" any more. You have to think it out and accept the ones you do because YOU decide they are good values to keep. Not just because someone else says so.
You have kept the ones that still apply, discarded the ones that no longer apply, and possibly added a few new ones to help you navigate your current life.
That doesn't mean you have to give up your religion or culture. It may mean you have to come to it with different understanding... like what parts are great about it and still fit with your current life and what parts are limited, and what parts just simply no longer apply.
If it is you who is calling yourself "sleazeball"? Beating up on your own self being your own bully isn't going to help you heal. There's taking responsibility for what you did wrong and feeling remorseful about it. And then there's going overboard with it and being your own bully constantly kicking your own self down. Compassion and forgiveness could include your own self too.
If leaning on 10 commandments isn't helpful right now because you end up beating your own self up... how about leaning on Catholic virtues? Maybe focussing on things like temperance, hope, kindness, faith, courage, knowledge, fortitude, etc could be more helpful to you as you navigate all this.
If you are struggling in cheating recovery, and struggling in realizing you may be poly, and struggling in your marriage, and at the same time, struggling with your faith? I could imagine you feeling a bit lost and/or overwhelmed.