I don't post here much... I just usually lurk.
But I couldn't read this and not respond - I had the exact same thing happen to me!! It was exactly as so many of you have described... about 30 seconds before let-down, I'd get this huge, horrible rush of icky feelings - for me it was some sort of mix of dread, panic, hopelessness and other things I couldn't really describe. It was one of the worst things I've ever felt, and I seriously thought I was the only one.
It lasted a long time for me - over a year - but it finally went away, and we're going on 27 months of nursing now. I'm pretty sure it was related to PPD; though I never have talked to anyone about it, I think I've had some level of depression going on for quite awhile now. It's encouraging to hear so many if your success stories in dealing with depression.
OP -- I'm glad to hear from your last post that things are getting more manageable and that you're feeling a bit better. I hope things keep looking up.
Thank you for posting about this - it really does help to know we're not alone.