DEAR ABBY: I am an attractive woman who has been married for 30 years. I think my husband has been cheating on me for most of them. Through the years I have seen the telltale signs and confronted him many times. But he continually tells me no, he would never do anything. I have tried hard to stay with him, although I feel stupid for doing it. You see, my parents were married for 62 years, and I ha…