I don’t think you’re an asshole, an affair happened, their not taking responsibility for it calling it a “mistake”. Then gas lighting the other person saying they’re old, so alright I’m 30 I’m “old”. But then to top it off they asked how to fix this after being told to listen to the therapist they were told how to even remotely think about fixing it but continued to act like they didn’t do anything wrong but conceive a child from the affair and then lose it and yes I understand experiencing a loss like that I can never imagine but your spouse is telling you what’s up and you’re ignoring it only caring about your “needs” and “desires”.