Have you read my Article posted aday ago on why Women do not like to have Sex. You can see the Link below:
Was this always the case? Was she interested in Sex when you got married? There could have been some emotional trauma that she could have undergone, like death of her loved one or miscarriage etc. There could be any number of reasons.
Your trying to find another woman foer sex, will further affect your marriage. You need to look inwards and not outwards. We are hearing your side of the story. What about her side?
You have to be patient. Involve some Senior that she can trust who will be able to communicate with both of you and not be biased. If you do not want to involve outsider, then try to go on vacaation together and spend quality time with each other.
You can also see a Sex Councillor, who is reputed in your area. He may suggest councelling Sessions and some Medication.
Sex is a thing that is difficult to speak to others and they will not understand the problem. Often there is a mismatch in sexual interest between partners and you may have to live with the problem.