Hi! I am going on my first cruise in a few months and asked my gyno what I could do to insure that I don't have my period during the cruise, I apparently cannot take birth control pills because of high blood pressure, and so he prescribed Prometrium 200mgs. I began taking them yesterday and will take them for 12 days. The problem is, the Doctor didn't tell me what to expect with this. Is this going to start my period early or later? Thank you all for any help you can give. Lisa :o