How old is your boy?
Do you have go-grow clock, as they not only help teach kids about when to sleep (there's a pic of a star at sleep time, the sun during the day) but you can also set it up as a night light too - we found this really helped when our first girl was about 3 - not sure kids get it unless they're about 3 or older (heavens knows i've tried with my 2 and a half year old girl!).
Have you got another baby sharing your room? He might be jealous if so? And that separation anxiety is a nightmare - currently experiencing this when dropping my toddler at nursery!