Here's a couple ideas before you go venturing off to check to see if the grass is indeed greener:
1) Has your husband had his testosterone levels checked? Male testosterone declines significantly, in a linear fashion, starting at around 25 years old. It is believed that HALF...50%...of men over 40 have low testosterone levels. Believe me when I tell you, this makes a HUGE difference. Get him on 100-200mg of testosterone per week and he'll be chasing you around the house with renewed fervor.
2) Do whatever you can to get the communication flowing with you and your husband. Most problems manifest because people forget how to talk things out. Voice your concerns, and allow him to voice his. It's imperative to keep ego's out of this, especially on his behalf, as guys can be stubborn with feelings. But also be open to the possibility that MAYBE you just don't do it for him anymore either.
The classic, no-nonsense, OmahaBeef approach:
A) Be classy and think twice, nay, thrice about dropping a steamer on your Vows like this. Take the grocery-store novel mentality out of this and use logic and reasoning rather than emotion here. Successful women THINK before they feel. Women who FEEL and not THINK got 3-baby-daddy's and divorce/credit attorneys on speed-dial.
B) Be wary of any man who claims that he is "in a failing marriage" and also 11 inches long. Better yet, be wary of any man who says he's EITHER at such a "conveniently inconvenient" time in your life. (I've got some beach-front property in Nebraska I can sell you.)
C) If you MUST go through with your desires (which you don't), fess up to your husband...come clean. If your going to fuck things up, try to fuck them up with as much honor as you can salvage.
D) Last but not least, and I can't reiterate this enough, THINK.
My methods are rough, but they won't steer you wrong....
...OB