I think she's cheating on me?

My wife has been leaving me alone with our kids the last few nights. she doesn't roll in until 4 or 5 am and she's usually laughing and plastered. this has been happening for three months now. she has cancelled many different appointments with me and we hardly talk anymore. what's going on? is she cheating on me? and why is she being so neglectful of my kids? i don't care if she treats me like garbage, i expect that, buty don't shortchange my kids!