You're falling by the way-side of the married peoples' Interest group. Once married and past the "Honeymoon" phase, and whilst moving nicely along the "I'm-realizing-I'm-stuck-with-this-same-human-forever-so-I-may-as-well-get-comfortable-and-fart-all-I-want" phase, your interest level rarely changes from the level known simply (but accurately) as "meh". "Meh" is usually accompanied by a shoulder-shrug and a dry, very-little-effort-as-possible-attempt to engage in what was once some pretty mind-blowingly great sex instead of the "suck, lick, sex, alright, I'm done, <snore>". Of course, this was back when your Interest was in the "Marvin Gaye, oooh yeah baby, let's get it awwwon!" phase. The only way to add new Interest is to engage in some type of marriage-counseling session with a woman therapist who hates men and secretly works toward freeing all spouses from the one true spirit-breaking and emotionally bankrupt and draining deity known simply as "husband" so that she may increase her own chances for happiness in her all-girl (confused as they may be) dating pool consisting of newly-single women that really aren't' sure what just happened - OR - convince your partner to watch a little bit of porn with you. Be sure to choose one with a good looking guy and no anal scenes...this just freaks women out.
Oh...wait, you're not married are you?