One truth is that if there is no one around...i mean if there are only one man one woman even a blind woman is the queen.. am not saying u are the one but as a wife u deserve to be a queen provided u meet all his needs or marrying you.
unhappy marriage is a nightmare in every body's life. when we are not happy in bed mean we are our life is sucks.
Therefore ignoring you sound like he got another alternative . i don't know what he would react if u ask him to get a medical advice on his sex behavior.
I do suspect infidelity so you better try to find out what actually is going on. i am not really sure whether your marriage was LOVE or Arrange marriage... if it was the later then this is the result of many.
any way i just wish you can find out the truth about him before taking a next step.