Is there a safe way to lower my sex drive?

Im 30 yrs old, been married for ten years. Wont leave my wife bc of our children. Shes a good mom, and a decent roommate, just not someone who is close to me. I have always tried to go the extra mile for her in bed, giving her multiple inner orgasms, and always atleast one outer before I take get mine. Yet the feelings have never been mutual. Her being a full time college student only compounds the problem. I have sent her flowers for absolutely no reason, I still treat her as a gentleman should. Now, I am also having problems with both of my knees. Even just fifteen minutes of sex (with me doing everything which is normal) is quite painful. Its just not worth it. A french kiss complete with forplay when the kids are asleep is just "sweet time" to her, not remotely erotic even though I am obviously turned on....I need to turn my sex drive off...HELP....