When you love your husband and he starts wanting to be alone and refusing to be close to you there are several things you can do to try to save your marriage. There's always a reason that someone drastically changes his or her behavior. Finding the reason is your first challenge. Then you can figure out if there's anything you can do to help.
The reason may have nothing to do with you. He may be facing some sort difficult challenge and be depressed because he feels powerless to manage it. Men have a hard time talking about their feelings and sometimes the mounting pressure leads to depression. Is he withdrawing from everybody or just from you?
He could be withdrawing from you because you have done or said something that he doesn't like and he doesn't know how to talk to you about it. Sometimes it's something physical like gaining weight or not taking good care of yourself. Maybe he feels that you're pressuring him to do things he doesn't want to do or not leaving him enough personal time and space. Sometimes a pattern develops when one spouse feels smothered and wants space and causes the other to feel abandoned and act clingy.
It's also possible that something worse is going on. He could be having an affair with someone else and getting his physical closeness there. He could be bored and angry or feel trapped. He could be spending his time watching pornography on the Internet.
If you haven't asked him about why this behavior has changed, you can start there. Since he's withdrawing he may not answer your question. You need to start to notice anything that's a possible clue to his behavior. It's easy to not pay attention to things we don't really want to know about so this may not be easy. Do it anyway.
A marriage counselor can help you both understand what's going on and what to do about it. A step you can try before you see a counselor is to learn to act differently yourself. "124 Tips for Having a Great Relationship" is filled with useful information about how to do this. You can get your copy at http://www.YourGreatRelationships.com .