This is sad to read. I am almost as old as you - 41, and I had a kid when 40, and my wife 36. The kid has been the greatest thing to have happened to me on a personal level, after we got married 8 years ago. We struggled a little but persisted and eventually got there.
I remember a conversation with the doctor who helped us - when you want to bring a kid into this world, especially when you're having trouble doing so, you have to want to do it 120% - you should never be short on will.
If you are regretting your earlier decision to not have kids, recognize that you have changed, and make the subtle shift in your mind to want to have a child. Dream about the boy/girl and what kind of life you'll build around him/her, and what you and your partner will do for them and with them. The dreams will spur you to action and the action will shape your dream into reality. Good luck.