Blame after loss

I lost my son at 10 days old. It seems like one of the hardest things for me while grieving is the blame that I've put on myself for not being able to save him. His cause of death states hemorrhaging, NEC, and colon perforation. We are awaiting autopsy results, which my husband acts like is going to be the holy Grail in his grieving process, but I feel like it's just going to further condemn me. As his mother, I should've known something was wrong before it became life threatening. My husband wasn't able to be there for his birth, 10 days of life, or his death. He was able to bring his ashes home from the funeral home with me, but aside from that I have endured this journey completely alone except for my 1 year old son (our boys were born 15 months apart). I had small concerns with his eating habits during my 3 day stay in the hospital following my C-section but they weren't very worrisome and easily dismissed by the nurses. He was very sleepy on the second day (probably a side effect of the anesthesia said the nurses, as long as he is still nursing, which he was). He spit up a lot the evening of the second day with a little bit of green in it (it is probably just colostrum and some of the amniotic fluid, it's not green enough to be concerning said the nurses). He nursed more frequently at night and not much during the day, was still peeing and pooping so I assumed he had his days and nights mixed up, just a sleepy baby. I took him to the ER 2 days before he died because he was obviously not fine. Distended stomach, listless, his breathing was shallow, skin color had changed. He was life flighted to a children's hospital where he underwent surgery for the colon perforation, and then surgery was attempted to remove more of his dead intestines etc over the course of those 2 days. I was able to see him in between operations and the last one his liver wouldn't stop bleeding which was ultimately the end for us. They allowed me to be in the room the whole time they tried to get the hemorrhaging under control, to no avail. I replay this scene and holding him after multiple times a day, every single day, and every night trying to fall asleep. Do you ever stop feeling responsible? I see people mention blaming themselves, but somehow I feel like I am solely responsible for this happening because he quite literally had nobody else and I dropped the ball. I participate in daily activities, because I have a living son, so really no other options, but I feel like a ghost myself.