ashamednamechanger, I have been in exactely the same place than you. I've had PND with dc1 and didn't bond with her for a long time (I mean years).
One of the best advice was one I found on here in the adoption threads: 'Act as if you love the cgild and you will learn to love him/her'. So I set off to learn to love that child as if I had adopted her (Strange I know but this is exactely how it felt to me at the time :().
I also found that my approach to parenting needed to take this situation into account. 'How to talk' and 'Unconditional parenting' have been the 2 approaches that have worked for us, probably because she (and me!) needed a parenting system that took her needs into account (more than for another child perhaps). I more or less stopped any 'punishment' (so no naughty steps etc...) because they did widen the gap between us. So I had to find other ways to parent her. Eg, I knew that being sat in a train would be difficult and she would start playing up. So instead of having a go at her, threatening her etc... I have always ensured that I had something with me to distract her. I've kept an eye on what was going on and took some action before she started to be unruly. etc....
I always ensured that we had some one to one time together, undisturbed. Ideally 10~15min each day (even though I haven't managed to do that all the time). And we did together what she wanted to do. When she was little, it was about playing with dolls. Now she wants to 'talk with me'.
When things get out of hand and there are more time when she is 'disobedient', I know I need to spend more time with her, cuddling, playing.
Eg when she was little and she would get really angry and start hitting me, I found that she was doing that as a way to get some sort of physical contact with me. So I just said 'No' or 'No hitting' in a very quiet voice and cuddled her instead.
I also learnt that praise needed to be real to have any effect on her. Telling her 'I loved her' when I didn't quite feel like had the opposite effect. She got quite cross and meant she didn't quite believe me when I praised her (in good faith).
TBH, I do agree with a lot of the comments up thread but rebuilding a relationship IS hard work. You need a lot of determination and a lot of patience (It took us a long long time to 'get over' that) and I know that even now there are still some 'left overs'. She is still quite insecure about my love for her due to the insecure attachement when she was little, even though I can now say I do love her the same way I love dc2.
If you want to go and see a counsellor, I would really advise you to find a psychotherapist rather than 'just' a counsellor and to ask him/her if he/she has some experience in dealing with PND and children with insecure attachment. This is a traumatic experience and you need some good advise re your parenting/behaviour towards your dcs that will go further than mainstream parenting techniques iyswim.
I really wish you a lot of courage. It is really hard work but so worth it at the end of the day. I did work for me and dc1. It took time, a long time, and in some ways is still work in progress. but as time goes on, it gets easier and easier and you can start relaxing. Gone are the days now when I was watching my every move and I can enjoy being with her the same way I enjoy being with dc2.