I find the same as Hope when it comes to PEM also being able to creep up and accumulating over time esp over periods of 2-3 weeks. With only just going over ones limit, it may take time to notice it. Thou you love to dance, dancing isnt a good exercise for ME/CFS. You are better off doing something like yoga (but not in a class as any exercise you start doing you need to SLOWLY build up and maintain at slight increases to see if a level is fine. Class situations dont really allow for that). I really hope at this point you dont decide to do part time work.. it sounds as if you need to work out where a stable activity level lies for yourself first.