am in so much pain after loss of my baby

i gave birth to my baby son at just 23 weeks and 2 days in gestation and my son was sent to NNU i had a spontaneous birth and before i had slight bleeding and rushed to the hospital the doctors told me they could see the babies membrane and that i was dilated so they rushed me to labour ward where they kept be head down to gravitate my labour but it just got worse and worse to the point of giving birth on the 19/05/2011 at 00:59 hours i had a baby boy and he was sent to neonatal unit where for 9 days he stayed in intensive care and he was fine for the last 7 days but 2 nights i was rushed in as my baby got a skin infection and then on he's last living day he got a gut infection called Necrotizing enterocolitis which made him ill and the doctors said they couldn't help him any longer so they said we need to think about taking off all he's help he wont live long so would you like to hold him for sometime and then we will take off he's breathing machine and he will die we where in shock and i said wait a few hours and then if it's the same then ok but he remained the same so he died in my arms as i was screaming in shock after he's death my feeling went numb the nurses bathed him and dressed him and i took him into my room and spent hours with him alone with my husband till i felt like i couldn't see him dead anymore.
now i have to arrange hes funeral  as he died on friday 27th may 2011 and on that day the doctor asked if they could do a full post mortem but i said no he suffered enough.
doctors have my placenta and are testing it to find out why i gave birth so premature and if it will happen again and i have to see the doctors aswell to talk about why i did so and why my baby didn't survive 

dose anyone have any idea what could have happened to my baby or me for that fact could it be caused by major stress or cervix wasn't strong enough?

i also had a postnatal womb infection could that have been the cause aswell?

thanks for your time