2 yr old son has been really good napper until last weeks when he has just screamed hysterically when I put him in cot in afternoon. Eventually falls asleep exhausted in buggy in afternoon 4ish but is really becoming overtired and cannot cope without this afternoon nap. Don't know how to get him back into it - grateful for any tips!We had a new baby 3 months ago which I think has affected him more now than when he was born.