Oral on period

So. my fiance has over come his fear of having sex while I am on my period. Well, he asked me if he could eat me out while I was on my period...(which totally shocked me as he very rarely does it anyway....) I didn't know how respond... I'm not sure what to say. And I'm sure I sounded stupid to him because he asked me what it tasted like... I was just like.. um... I dunno... PLEASE HELP!!!