Why is my wife not attracted to me?

U know, I work out, I have a nice body...six pack, slim, pretty easy on the eyes I think, but she doesn't seem to jump me the way I desire. I understand we might b very different when it comes to ual desires, pda's and the sort, but I've worked hard to look nice for her and to almost no avail. She is not as thin so I wonder if it is because she feels insecure in her looks, but I constantly reure her how much I love her. It seems to b beginning to affect our life. We've been married for 7 1/2 years with two children, y now after all this time am I even less interesting to her if I look better than before?!