hey mamasgirl - yup, i have fasted during my period. i don't ever weigh myself on a fast but when i have my period my clothes do feel a little tighter than normal and then it balances out after the first few days. this is just like how it is when you are not fasting - fluid retention, hormones blah blah.
try not to worry about daily weight loss because the body knows what to do, and will always do what it needs to do first. if the body is healing something, you may not lose any weight for a bit - but just know that you are working towards much better health.