Hi OliEli's Mum,
I don't know of any studies on the topic, but I do share a similar experience. I suffered from postnatal depression for 2 years before I was diagnosed and it took me a little over a year after that to really be feeling functional. I was very worried about the damage my passivity might have done in those 3.5 years, but dd (now 4.5yo) is a happy, healthy, confident little girl and she and I now have a very close and happy relationship.
So be kind to yourself

It sounds to me like you're a great mum doing what you can for your kids.