OP,
Yes, I have been in a similar position, albeit from a different angle.
In my case, my wife and I had made a joint decision that neither of us would use contraception, and try for a third.
My wife fell pregnant at a very dark time for her at work (she was being bullied) and when her mental health was very poor (depression and anxiety disorder) and decided (over my objections) to abort what would have been our third child at 6 weeks. I tried twice in the week after she found out she was pregnant to change her mind. I failed.
I regret, deeply, not trying harder to persuade her to change her mind. I regret not reaching out to my dad (who she respects immensely) and her sister, as they my gut tell me they may have convinced her that, with the combined support of myself and them, she could have that baby.
That was 6 years ago. She has only recently told me how deeply she regrets her decision. Whilst she has never said it directly, I am fairly confident from other statements she has made about how mental health impacts decision making that she has realised that the decision to abort was made in a dark place, in response to a tough situation and when her judgement and thinking were, at best, clouded.
I still cry a couple of times per month about it. Stories about abortion law reform trigger me. It's hard.
I suggest getting counselling. Our church pastor was amazing (very non-judgemental), and a psychologist helped me turn anger at my wife into "normal" grief, if that makes sense.
Take care of yourself, it's OK to regret what you think or know, with the benefit of hindsight, was a mistake. I find it helps to acknowledge that we can make mistakes, acknowledge the reasons WHY we made those mistakes and forgive ourselves.
In my case, my mistake was to think that being a husband who respected his wife's bodily autonomy meant to stop talking to her about her decision, once she had made it. My mistake was to not reach out to our mutual support network until she was literally at the clinic and I was crying in the car.
I realise those mistakes now. I understand I was trying to respect her decision, even if it was one I profoundly disagreed with and one that was made when her rationale decision-making capacity was at its lowest. I take some comfort in that. Be gentle on yourself. We make mistakes, it's what we learn from them that matters.