i see from your signature that you have a toddler.
Is it possible that your wife has postpartum depression?
I ahve read that depression affects sex drive; but usually running fights depression too.

By the way, I used to race a half marathon once or twice a month until my wifes affair. I sometimes place in the age group. I love running.

Is your wifes running friend a "good" friend or a "toxic" friend?