What do I do

I'm having a problem when me and my fiancé first started we where like rabbits going at it 2 to 3 times a day and all those we still have sex almost everyday it's like she dose it just to make me happy she will huff and puff about it to the point where if I want it I have to wake her up in her sleep just to avoid an argument cuz she's to tired to fight back what's up with that we are trying to have a baby but it's like my sex drive is infinite and hers is almost non existent now I go above and beyond to make her feel special from surprise candlelight dinners to flowers for no reason to little notes on the table when she wakes up what should I do