Newborn not sleeping in his cot.?

my baby's three weeks old, and he will not sleep in his cot. he use to sleep kinda well next to me but its real cold at my house so he couldnt sleep with me anymore as i needed to use the blankets. now he will only sleep when hes in his bouncer or laying on my chest! i spend most my nights awake on the couch so i know he wont fall off my chest. does anyone know how i can get him into his cot so i can get some sleep?