MotherFunk, you came home after a day. Good maternity care would have meant you saw a midwife on the next day, and she would have checked the feeding was going well - and the day after that and the day after that. You would have been informed that your baby should be pooing and weeing, and by day 4-5 your baby's poos should be turning yellow. Your baby would be feeding enthusiastically and often, day and night, and you would have learnt what signs to watch for,in his feeding behaviour.
Stress would not affect your milk production, any more than stress stops the circulation of your blood or the production of lymph or your nails growing....you produce milk as a direct result of having a baby and it is totally physiological.
Sometimes, mothers' milk comes in very late indeed - but these (rare) situations can be spotted, if the mother herself has been told how to tell if all is well or not with her feeding - long before the crisis hits at day 6 in your case.
Not seeing a drop of milk is a sign all is not well - someone should have been at your house seeing that all was not well, or else been summoned by you, because you had seen these were danger signs. On day 2-3. someone should have been helping you express colostrum ie as soon as it looked like things were not going well.
Just telling you to persevere without fixing it is not a help - as you found to your cost, when your baby was weighed.
To have lost three pounds from his birthweight is a truly massive amount - and it was, as I say, your poor maternity care that led up to it, and not your stress.