I think I want another baby. Advice?

Hi all! I'm new here and have struggled to find anywhere to talk to any other birth parents. In Feb this year I gave up my son from birth. My decision came from his father not being around, my borderline personality disorder and already having 2 prior children with another man, my daughter, 8 and my son, 4. My 4 year old has global development delay and can be difficult most days, needless to say it was a difficult and lonely pregnancy resulting in me relinquishing my new born. It's been 8 months and my relinquished son's dad has been around for the last 6, we are rebuilding the relationship and healing as a family after the decision I made. My problem is is that I feel I made the wrong decision. I am happy that my son is with a loving family that I chose and have contact with but I feel incredible emptiness at the loss of the opportunity to parent again, having 2 children already I know what it entails and I feel that loss heavily. Most would say why didn't you keep your son if you want to parent so much but at the time I was very alone and my mental health was very poor as I stopped taking the medication required because of effects on the foetus, I felt I had no chance at bringing this boy up well with the strain on myself alone. But since his father has come back and our family has grown in strength I find myself longing for the chance to parent with this man. It is not a feeling I welcome as up until this last month I was adamant I would never have any more but as time passes I truly feel it was our fate to do this together after making such a mess of our situation before. I feel we have a second chance to go back and do it right now we both understand the weight of our actions, can anyone else relate or give me some advice please? I apologise for the length and vagueness of the post Lol, I just need to talk to someone who can relate!