Difficulty conceiving at 49 & Relationship strain

I am a 49 year old woman that have been trying to conceive for the past 6 years. I have been to doctors having all types of test to see if anything besides my age would be the factor of why I have yet to conceive with my husband. According to the test and doctors I am ok still having my normal cycle . It has become a topic with my husband now to where if it is him it’s hard to talk about because he feels it has nothing to do with his sperm health. I do have a now young adult son from a previous relationship, but my husband don’t have any child .While all the time I think it could be me I have been thinking throughout the years to let him go and live his life because he deserves to experience fatherhood even if it’s not with me. But on the other hand he will bring up topics of how do I feel about polygamy. Which I am not with nor do I support. He would then say he never thought of this but the situation is making him feel this way. So without him saying it he believes the issue is with me even though I have had many test to prove otherwise. He want me to pick someone which I will not do. The fact that I to want more children it’s heart breaking that he’s willing to lay down with another person to hopefully get a child. Even though it’s hurtful that I wouldn’t be the one who’s pregnant my compromise to this situation was to look for and go through surrogacy which don’t include physical contact. Yet he don’t believe in that which only leaves me to believe that he just want to be with other women and disguising it as a wanting a child, which makes me sick to my stomach . For some reason he feel because I already have a child. I’m OK, but I’m not OK. I don’t think he understand the fact that to love somebody and want to have children with them and it’s not happening how devastating to me that is. It’s not that I don’t want him to be a dad. I love him enough to let him go because I don’t think I can be with him in that way anymore if that’s something that he choose to do choosing to be intimate with another woman. Have anybody else been through this or going through this? I just need somebody to talk to.