There is no problem with taking enemas during your period. In fact, this is an excellent time to do enemas and many women find that a warm water cleansing enema a few degrees above body temperature helps to relieve menstrual discomfort.
As far as the frequency of colonics, I wouldn't suggest more than two the first week, or more than once a week for the next 2-3 weeks. Eventually when you feel that your colon has been completely cleansed, a monthly colonic, plus enemas at home as needed are not a bad option to help maintain optimal health.