Hi there ~
The white layer underneath your prepucial skin or foreskin is the collection of secretions from the glands around the glans penis
. You read right about smegma
and it is exactly that. You have to get rid of it and make sure that you clean your glans everyday by pulling your foreskin backwards. I also think that you might have phimosis
and need surgical attention. Please see a surgeon who can help you with the surgery and have a good sexual life. I hope this helps.
Take care and have a lovely day!