You've given us a little information, so what we can do is take a stab at what might be wrong. Other posters have done that. I'll throw out a few possibilities to.
Do you think she might be bitter or upset with you about something in the past? Maybe she expected something of you as a husband, and it didn't work out. Did she expect you to be CEO of your company by now? Did you have a life goal together and you haven't met it yet? There could be some issue that's been allowed to fester and it's turned into a respect issue. Again, just another stab in the dark.
If you are too much of a 'nice guy' that may be counter-productive, too. Husbands are to love their wives. But some men avoid confrontation with their wives over important issues and treat them 'nicely' instead of providing leadership, accountability, etc. It's an easy trap to fall into without realizing it, because you want to be nice to your wife. But nice and loving aren't exactly the same thing every time. For example, if you have sex so rarely, you can be displeased about that and show it. If she ignores you in other areas in your life, you can communicate that to her, and make it unpleasant for her to be that way. You don't have to be a pushover about it.
Again, just a stab in the dark. You'll need to really talk with her and somehow figure out what the root of the problem is. Have you confronted her about being so apathetic and not behaving toward you, physically and emotionally, as a wife should? Before getting into your grievances against her, how about asking her in what areas you fall short as a husband. You know that guy who said I am my own worst critic? Well, he probably wasn't married. Your wife will likely think of some areas you can improve. And if you ask her point blank why she seems apathetic toward you and talk about it for a while, she may just tell you.
Whatever the problem is, another important piece of advice is to regularly pray together. You can also study the Bible together. You can even pray with her about the apathy issue. Humble yourselves before the Lord and ask for help. Marriage problems are a small thing for the Lord to handle. If you both come to Him humbly in prayer asking for help.