Breastfeeding and antidepressants

Hi there,
I gave birth to my second daughter two weeks ago. I had crippling post-natal anxiety after my first daughter and unfortunately on day 3 it came flooding back this time - since then I have been up and down, good days and bad days. I've been hoping that it's just hormones that will settle but I am preparing to deal with it as post-natal depression / anxiety if I need to.
The whole premise of my problem following my first daughter's birth was around poisons / toxins / carcinogens (I lost both parents to cancer not long before she was born). I perceived danger everywhere. I never took meds because I just saw them as another toxin, and I breastfed my daughter until she was 21 months. Unfortunately it's only really now with hindsight that I realise how I was fairly highly strung during my second pregnancy, with echoes from the post-natal anxiety following me through the whole pregnancy. I then got fixated on the fact that my second daughter was only 6lb11oz, 14oz less than my first daughter - the midwife said that it was unusual for a second baby to be less than the first. Plus I am a big lady and always expected I would have big babies. So I have convinced myself that I exposed both my daughters to my stress and anxiety in the womb (the first time round I was grieving my parents) and then spent days googling what it meant for their brain development. Cue all the horrible statistics in the world, higher risks for schitzophrenia, depression, autism, etc etc. And my brain catastrophising the whole time. Completely convincing myself that they are damned for a life of depression and anxiety - which have plagued me my whole life. I also suffer from dermatillomania.
So I am prepared this time to take the antidepressants. But I am also aware that there is a paradox in that it could make me feel like I'm toxifying my daughter through the breastmilk. I wonder if anyone has any experience with this or has any information on the long term effects of breastfeeding a baby whilst on antidepressants. Thank you very much for any advice you might have.