You can take norethisterone, which is a synthetic progesterone, to delay your period over your honeymoon, but as it will interfere with your cycle, and thickens your CM, I think it's unlikely you'd get pregnant while using it. I don't think it'd be impossible, though if you're expecting AF during your honeymoon you'll have missed your fertile window anyway. You can get it on prescription, and I *think* you only take it for the few days before your AF is due and through the time you don't want it to appear. Do you know for sure your period will be due during your honeymoon?