I am so impressed with you sharing this you story with us as difficult as it is. Welcome to the forum.
I understand being in a marriage where both spouses go to church and I understand being a wife. I am also a counselor and have spent time with couples helping them in their marriage.
With that I agree that you need a wife who is going to love you sexually and no sex in three years is difficult for you. Who could bare it? I do not promote masturbation or pornography. But I can see your yearning for deeper affection.
Now about your wife. Are you following up with the counselor on her going to the GYN. If she is not making effort patience is needed. She needs to be accountable by someone besides you to prompt her to go. I suggest contacting the counselor again if you haven't. You should not, I repeat you should not be in a sexless marriage. I am happy you have been faithful to her this far.
Another thing this check up system is one sided. I feel she should also be spending more time seeing what she can do to fix her side of the problem. Between us she may have a lack of honesty as well. Some women just say sex hurts when there may be a deeper issue like she does not want to get pregnant again. The first may have been too traumatic. or honestly they don't want to mess up their body. There is definitely a fear that needs to be addressed. It could be a host of things like birth control issues. Or hopefully she is not seeing some else.
Whatever it is you will have to get to the bottom of things address your needs and let her respond. True love will do whatever it takes. Then make your own decision based on responses and what you feel is best.
Hope this helps.