My wife is not conceiving. I want to marry another woman, how do I tell my wife?

I am in my late forties and my wife is 39. We have been married for 11 years now without a child and even though we have been very hopeful and prayerful, a child is not coming forth. My wife and I are both fine, medically. We have been to numerous hospitals and we have had contacts with many gynaecologists and they all said we are fine. I love my wife so much but we are not getting any younger. I am thinking of remarrying and I don’t know how my wife will receive the news. 

The pressure from my family and friends is becoming too much. In the past few years, I have been faithful to my wife and I have shielded her as much as I can from pressure by external people. She has also been a good wife to me and that is why I am finding it more difficult to marry another wife. It may hurt her and weaken her spirit and I don’t know how to handle it. We are getting old and we don’t have any child to call our own, even if it’s just a child. 

I want a child and that is why I am considering remarrying. Two years ago, she opted for adoption but I disagreed. I am not open to adoption because of certain reasons. I want to know the origin and true identity of whoever I call my child. I do not want to pick up just anybody and start calling him or her my son or daughter. I know that there are genetic traits that are passed on to kids from their parents, some of which are bad traits like stealing and the rest. I don’t want to raise a thief or someone who has questionable character and that is why I disagreed with her opinion on adoption. 

I don’t know if she will despise me for kicking against her opinion and going ahead to marry another woman. I have plans of taking care of her as I have always done. I’ll respect her and ensure that whoever I marry respects and treats her well. I don’t know if there’s any best way to inform her. I know the news will reach her as a shock and that is why I want to do it in a gentle way, at least to reduce the pain she will feel. So please I need suggestions. How do I tell my wife about my intentions of remarrying? Please help.