Need Advice

Well ive now had my expanding retainer in for 6weeks.... Things are certainly starting to move. I can feel a real difference when i remove my retainer. My bite has completely changed and feels weird. Not really noticing to many changes from the front veiw tho.

Ive been suffering with really sore heads for the past week. My dentist says it is likely to be the retainer that is causing it because my teeth are starting to move. I cant seem to take anything to get rid of the pain Does ...