Since we had our third child 5 years ago my wife will only have anal sex. She told me that vaginal sex causes a lot of discomfort, and I can tell she is in a lot of pain.  She enjoys oral but will only allow me to penetrate her anally.
My question is that we are intimate 2-3 times a week (usually), and I worry that we may be doing serious damage to her rectum? She is no longer "tight" at all (but I dont have the heart to mention that) anymore and has issues ever now and again with getting to the bathroom, but refuses to talk about it with her doctor.
She has been to the doctor several times but will not have the surgery her doctor suggested for the vaginal issues. I have never been a huge fan of anal sex but my options are limited!

Please feel free to offer your advice as we are both 38 and been together for 13 years, but I feel like a "gay guy" (NO DISRESPECT), for the last 5 years.