Balotelli - I think there are some really good points made so far, especially you trying to get to the route of the reason(s) why she doesn't desire sex and working on these (if she is willing) prior to making any life changing decisions (assuming are leaving her? Affair?)
I would be mortified, as a woman, if my OH wasn't satisfied in the bedroom; likewise he'd be mortified if I wasn't satisfied too.
Someone mentioned earlier in the thread about compatibility from the beginning of the relationship and I do agree with this, which in my relationship has always been open about sex and the desire for it and talking about this when each other are horny/unhappy etc. Therefore, surely communication is the issue here, not lack of sex? Have you physically sat down and put your cards on the table about how you feel about your sex life?
Women and men do view sex differently to each other (from personal experience there is a pecking order of 'things' to do like work, cook food, housework, take care of dd..list is endless
) for men, it can be about "luuuurrrve making" but IMO is normally "release" too 
If my OH was unhappy, he'd talk to me about it and let me know how he feels. There was a dry patch (poor choice of words there!) during my 1st trimester when I was vomiting everyday and completely exhausted which resulted in the odd joke about him knocking one out in the shower, but that was only temporary and it was a joke- It concerns me that your wife is so blasé about telling you to pleasure yourself?!
If i were you, i would sit down and talk to her about how you feel. Of course it'll be hard for her to hear that your are unhappy and hurt by her blasé comments to wank "please yourself". See how she reacts (probably defensive) but show her how hurt you are by the situation to and how you are willing to do anything to help her enjoy sex and the connection from it and help her around the house too (certainly if she's using this as an excuse- which I'm sorry, some people do that).
A close friend (and shrink) once said to me: are you being lazy when it comes to sex, or do you genuinely not want it? If it's the first, stop being lazy, get yourself "in da' groove" and you'll enjoy it once you get started (which is so true for the majority of women out there IMO!!). But if it's the latter, then you need sex therapy or a new man!
From your posts, you sound like a lovely man and will be sensitive to any discussion with you dw. I can only wish you the best with your marriage 
Ps. I read your post out to my OH and he said leave her!! How men and women are soooooo different! Its a good job he's satisfied despite having a 5 month old dd! 