Why is he no more sexually attracted to me..?

i dont know what happpend to him ....it has been a month since we had sex...he comes from the office and gets very tired....i try dressing up sexy..but it doesn't effect him much...he will just smile at me...and that's it...i tried to even tell him once that lets do it tonight...and he was like..making fun of what i was sayin....no baby nooo..not a good thing...lol......and smiling away!! !!!!!!....still whenever we had earlier slept at night...he was seduced many times and we had sex...but now..it has been a month we had sex with each other..its not that i am frustrated or something....i just don't understand why..?? coz he is my love...and i want him to get into me...is it that he doesn't find me attractive anymore.. or what can be the reason...how should i approach him for this...