What do I do if I suspect my wife of cheating?

I am looking for advice on what to do if I suspect my wife of cheating. I have been uncovering little clues and I have certainly seen things that I believe are signs that my wife is being unfaithful.

I have always read that I need to be absolutely certain that my wife is cheating before I confront her. The problem is, I always believed that you can't just go with circumstantial evidence. I have seen some very weird coincidences in my life that I would have never believed if I was just told by someone else.

Just because she is acting distant does not mean with 100% certainty that she is acting that way because she is with someone else. It really could be that she is preoccupied by something else that she hasn't shared with me yet.

So far, the my biggest clue has been how secretive she has been with her cellphone. She always has it by her side now. My problem with accessing her cell phone is that she has a passcode on it even if I was able to try to check it while she was sleeping or something.

I am trying my best not to see things that aren't there, but I still just have that little "gut" feeling that she is.

Is there any question that I can ask her that isn't straight out accusing her? I would love to give her the opportunity to open up about what is bothering her or what has been going on.

I have always thought of my wife as loyal, and the thought of her being unfaithful kills me. My mind is so scattered because not only do I not know if she is cheating, but I am not sure what I would do if she was in fact being unfaithful.

I would love to hear feedback from anyone on what they did when they found themselves in a position in which they suspected their wife of cheating.

Thanks in advance