dehydrated baby😰

My baby was born on friday everything came out good. I was released on sunday i was BF but my milk had not come down yet    But people kept encouraging to keep BF and eventually it would come i went home and didnt give baby any formula. On monday he was more fussy then usual and crying but i didnt known what was wrong. As a first time mom you dont know a lot of things. Then i read through some papers and saw that i should take him to the er if he had less then 6 wet diapers. So that monday he only had 1 the whole day and as soon as i read that i took him to the hospital and he was admitted for dehydration and hypothermia and was giving formula. It was super scary, they had to drawn blood out multiple times it broke my heart. My milk did not led down until the next day. He was in hospital for 2 days and was on iv. I felt like a bad mom for not giving him formula and listening to everyone say colostrum was enough😔☹️ now hes a healthy baby.