Before you can change anything you have to come to terms with why your wife is cold and distant. It may be difficult to pinpoint exactly what happened that changed your connection with her but it's important to give it some careful thought. Consider when you two first were married and how she treated you then. Did she change after the children arrived? Does she ever make comments about the fact that she's dissatisfied with herself or is she struggling with some stress at work? Anything like this can have a dramatic impact on the way a woman treats her husband because he's the person she feels closest to and feels most comfortable with allowing her feelings to show. Unfortunately, that also means you take the brunt of her moodiness and anger.
You have to break down the barrier that your wife has built around herself. You're going to do that by overwhelming her with love and devotion. It's very likely that you've pulled back from her as well as a result of the way she's been treating you. That's understandable and to be expected. You have to break free from those feelings now though and put your wife's needs first. That's not easy when she's being cold and distant with you.
Start by telling her you love her more often. Help her more with the things that add stress to her life. Go out of your way to do things that will bring a smile to her face. That might include just calling her in the middle of the day to say how much you value her presence in your life or stopping to buy her a small gift on your way home from work. If your goal in life becomes making her happy, her entire demeanor will change for the better. Sometimes all a woman needs is to feel that her husband still appreciates and loves her just as much as he did the day he proposed to her.