Dear Amy: I’m a 35-year-old man. My wife and I got married in our 20′s, and immediately plunged into being “parents” to her niece, who moved in with us just before her 10 th birthday. We raised her exclusively and in my opinion did a really good job.

Our niece is now out of the house, and we have mutually agreed that we don’t want to have children together.

I am enjoying this stage of our lives. We are both successful in our professions and are physically active on the weekends – hiking, biking and skiing in the winter.

My wife has seemed down lately. She is picking at me over things that didn’t bother her before.

We finally had a heart-to-heart, and she said she wants to have an “open” marriage.

She laid out the ground rules and essentially said that if I didn’t agree to this, she would cheat on me. I definitely do not want to do this.

I feel trapped and don’t know what to do next.

Your thoughts?

– Hurt and Confused

Dear Hurt: I think your wife is likely already cheating, and is now trying to retroactively get you to agree to it.

Even if this is not the case, she has presented you with an unacceptable non-negotiable.

Preserve your dignity and get in touch with a lawyer.

You can email Amy Dickinson at [email protected] or send a letter to Ask Amy, P.O. Box 194, Freeville, NY 13068.