your worry about not having interest in sex is the important part ALONG WITH the lack of satisfaction from your partner.
so where to begin;
what r the circumstances of u and her= age, marriage etc
have u talked to her in depth and if not can u formulate a way of doing so (help is available)
has she spoken about this, will she join u in a discussion, does she feel upset due to this or maybe not at all?
best to u