i agree, you should definitely speak with her. try to keep in mind that she may be under stress (you didnt mention that so i dont know) or having body issues, if she doesnt feel sexy she's probably not going to act like it. im sure by now you know how to approach things with her so just be gentle, it's a tough conversation for both parties. you could also try something romantic, like going away for the weekend, lighting candles at home or even just finding a different place to do it.
best wishes!