Book a "date" with your fiance, for time when you won't be interrupted and plan an evening just spending time alone together - you don't even have to have sex, but maybe have a bath together, cook a romantic meal, light some candles and listen to some music, above all concentrate on eachother. Be gentle, and don't put pressure on yourself - so what if you don't want sex at the moment? Despite the unhelpful posts above, it really is no biggie and the more you worry the more of an issue it will become X