My Son Died In His Sleep April 5th This Year,

My son died in his sleep April 5th this year, I can't help but think that hi. Bleeding from his nose was due to suffocation - my son had such a strong necks for a 2 months. The first time I put him in the bed is when it happened - i also want to know if having a virus be a cause or cot death? He had diarrhoea 10days before he died and had an on going cold which the doctor would not provide medication due to his age - however they never advised me after him having a cold not to put him on his front as it could effect his breathing