bro, i feel for you. signing the contract thinking all's well and sex will be as great but...
why not give her surprise sex?
but before that, make her feel very comfortable by creating ambience and stuffs. find out the reason why she's not intersted in sex anymore through observation. no woman want to be treated as a sex object. so you confronting her may sound like the right thing to do...but indeed, it may have made matters worse..all i can say is try all the tricks you can and if nothing works...i wish you the best...