assistance please

My wife and I have been married for 14 years and have 3 small children under 8yrs. of age. I am 39, she is 37. Our marriage is very strong outside the bedroom as we share many of the same likes and dislikes. She is an at-home Mother. Our problems lie in the bedroom. I feel as though my wife has no sexual attraction to me, even though I keep myself in very good shape physically. She insists that her sexual desire is simply not as strong as mine. In our 18 years together, I cannot recall an instance when SHE initiated sex. It seems as though she is going through the motions during sex just because she knows that I want to have sex. There are times when she will loosen up and respond positively, but typically after having a few drinks...which is seldom. Lately i have found that when I am out of town traveling she is using a vibrator that I purchased for her a few years ago. This has me completely unraveled as it is a very strong indication to me that she wants sex, but is not willing or able to come to me for it. My wife is by far one of the most attractive women that I know and I am incredibly attracted to her and try to tell her as often as I can how attractive she is and how she makes me feel. She does not seem the type that would run off and have an affair, but lately I am questioning this as we see it happen all the time in today's society. Please help me understand where to go or how to deal with my concerns.

thank you...

An old Chinese proverb says: "Men are fire and women are water. Man's fire makes the woman’s water boil."
The sexual desire of a man can be turned on immediately by seeing a beautiful woman, whereas women can experience fantastic sex, but may need an experienced lover for maximal pleasure. Accept that you need to take the initiative. Continue to be attentive to her as if you have just fallen in love. Warm her up with a lot of foreplay and give her delightful orgasms. She will then have no reason to be unfaithful. A simple intercourse where the man satisfies himself with the woman’s body can feel meaningless for a woman.