It may not be that bad. I have used an Aloe Vera mouthwash in the past, not sure what others think.
Your main problem may be be your boyfriend thinking you have gone crazy, LOL! I spoke to a nutritionalist about 6 months back, her dad did a fast once and her mum threatened to divorce him after about 20 days despite the fact he was full of energy and jogging to work every day! But seriously, good luck on your fast, hopefully he will understand, and if he doesn't you can always point him here.