Bedding for babies

[LEWIS1996]

Hi there
Does anyone know what age you can use a duvet on a baby. Up until now Ive only used a sleeping bag for Mason but last night he woke up and was freezing, he ended up in bed with me. Im scared stiff to use blankets or duvets but are they safe now, hes 7 months.
Also is it ok for him to now have a teddy or security blanket in his cot. I know there not supposed to until a certain age but I dont know what it is?
Advice would be appreciated.

Love Pamx