@Nannewnannew - as pp said, you cannot know that picking your son up would have changed things and small comfort as it is, I hope you can find peace.
I regret not phoning 999 when I was having a placental abruption because I couldn’t accept that I wasn’t just going to go into labour and listened to all the midwives telling me it was ok. I lost my full term DD.
I regret staying with my husband when he tried to throw me out just so he could get with someone else (that he wasn’t even sure was interested in him). In a way then the rest of the awful things that happened to my two children (the stillbirth and my seriously disabled DD whom I adore but who has such a hard life).
I also regret not cheating on this same husband with someone I was tempted by. I thought I’d feel awful if I did. I don’t think I would have felt as bad as I do most days now