just so as not to hijack the nightdress thread too much! lol
went to the doctor who said she thinks it is probably a muscular thing... due to ds being much more active now and doing a lot more picking up etc etc. the pain isn't always in the same place, which backs this diagnosis up.
but she did send me for full blood count and thyroid test, and said that if it is still bad in a month or so then to go back.