Hey OP- just wanted to write with my support. I did have drops of milk when pg, and a bit of colostrum when dd was born in March, but it vanished after a couple of days- I wasn't able to squeeze anything at all out by day 4 & my breasts which had only increased by about a cup size, but felt much fuller than normal, had completely deflated! Couldn't see a mw until day 5 afternoon, and she had us rushed to hospital as dd was severely dehydrated, nearly 20% less than her birth weight & v low blood sugar etc. She was put on a drip & formula fed, and stayed in hospital for 5 days, so all quite traumatic. I'd had a fairly straightforward VB, though things were very complicated with DP- I wasn't sure he'd be able to make the birth- so things were stressful on that front, which could have been a factor.
Anyway- I managed to express literally about 5 drops of milk on day 5 & kept putting dd on the breast to encourage supply, and I did get a bit of milk through by the end of the first week, though I was never properly engorged. I saw a bf councillor & various drs/ mws/ nurses and people came up with a variety of reasons why the milk didn't come in 'til so late. These included stress as you've mentioned, but also:
Part of the placenta may have been left behind, so the milk-producing hormone didn't kick in. I don't think this was the case for me.
Or the latch could have been wrong at the beginning (it was OK later on, but this may have got us off on the wrong foot). DD was a bit snuffly when she was born, and blowing bubbles. I've since heard that if the baby is stuffy they can find it hard to latch on. (Since then we've used simple saline drops to clear her nose as and when necessary).
I think mostly the problem was that it was my first child, I didn't know what to expect & we started off wrong, but it took me a while to realise- when the milk didn't come in everyone I spoke to including bf-ing friends, family, various mws said "oh, it will be here in a day or two!" and I just believed it would. In hindsight, I wish I'd checked my technique at the hospital before I left- staff looked in on me bf-ing & assumed I was doing ok.
Anyway, I've always topped up with formula since then (she's now just over 3 months old) but have managed to bf in combination too. I don't know if any of that is especially useful or pertinent to you, but don't give up hope & make use of any advice & help open to you is my advice. Good luck! X