Your marriage sounds like its on the same path mine was headed towards before I took responsibility and started making changes. Our origin story isn't the same (Katie and I were not virgins and not outstanding Christians) but we were heading down the "sex isn't that great anymore" pathway.
First, stop comparing yourself. You aren't him. He isn't you.
Second, do you still want to be with her?
Third, if you're still in love and want things to work, look into the book "the love dare". It's a Christian book but it's not smacking you in the face all the time with bible verses and how you're no good to god or anything. I think anyone could find it useful, even atheists. Read it. Commit to the dare. It helps. I'm six days in and I'm telling you, it works.
"Regret for the things we did can be tempered by time; it is the regret for the things we did not do that is inconsolable." - Sydney Smith
Kyle: 27 year old male
Katie (rymmare): 25 year old female
Kids: girl: 5 years old, boy: 3 years old