Pitchounette - your post reminds me a little of my situation. When dd1 was born, I bonded with her immediately. When DD2 was born 18 months later, I also bonded with her immediately. But then something strange and unexpected happened - my bond with dd1 'broke'. It took me about six months to realise this, I had mild PND, but gosh those six months were awful. I was sure my dd1 was the child from hell. I looked at her and couldn't see my child, I just saw 'a' child, and I couldn't feel any love for her.
When I realised what the problem was, that I felt as if I had no bond with her, I could start doing something to repair our relationship, by positive parenting as you've described. Things are far better now almost a year later and I have two angelic daughters, whom I love equally. I realise that my bond with her wasn't broken, just invisible, hidden by PND. I am very fortunate that my PND wasn't serious and with help from family and friends I reovered quite quickly.
Things are so much better now, and I'm glad they are for you too.