Well you're not alone in this at all...it happened in my marriage, and many (if not most) other men's marriages too.
But it doesn't have to mean strife in the marriage, end of marriage, or even end of good sex in the marriage if you do things right...
Reason a Wife Doesn't Initiate Sex...
Before we solve a problem we first have to understand that problem. When it comes to the problem where a wife doesn't initiate sex there are many things that you need to know to realize that you're marriage isn't necessarily in trouble. But it also doesn't necessarily mean it isn't in trouble either. I'll explain more about that in a minute.
But first let's get some things straight. Your wife isn't initiating sex because...well...she's not like you. She's wired differently than you. Just because you're RTG (ready to go) as soon as you wake up until you go to bed doesn't mean that your wife will be.
Us guys get horny from every little thing every few seconds. It's just the way we're wired. We're externally motivated for sex, and so our brain drives our sex drive from a lot of imagery situations...and imagery is every darn place.
Your wife however isn't like that. She doesn't look at a banana and get horny the way that we might look at erect nipples on a mannequin and be RTG, or other simple things that make us nearly Neanderthals. Your wife is turned on by emotional circumstances. Intimacy, erotic stories, happiness, security...all of these are the things that turn your wife on... and ironically are the things that bore us to death.
So unfortunately for all of us men in the world who get annoyed because our wives don't act like the women in porn and are RTG at the drop of a hat, or the unveiling of a penis...we have to get over it and learn to play the game.
We have to realize that if our wives are feeling things emotionally then they're not going to initiate sex with you because frankly they're not going to be in the mood for it. In fact the most that we may ever hope for as husbands is that our wives will be willing when we initiate, and take those single digit times that they do initiate as a bonus.
You see a lot of guys will get mad at their wives, will take it personal, and will constantly badger their wives about them not initiating sex, but they won't do anything to make the woman want sex more, much less initiate it.
So here's where the problem lies. If your wife doesn't initiate sex... or more so doesn't want sex when you initiate it, this could mean that she has some hidden (to you) negative thoughts about you and your marriage. Which means that your lack of sex, and your wife's lack of interest in sex could be indications that your marriage is more trouble than you think. It could also mean that she would be much more willing and open to an affair with someone that actually made her feel more positive thoughts.
So if your wife doesn't initiate sex then it could mean you're going about things wrong. It could also mean that this is becoming a deep seated problem in your marriage.