Lost Control in Unexpected Places

I just got through a messy divorce and am trying to figure out who I am without my former partner. One day, while at work, I was alone in the office, my thoughts turned back to those intimate moments with my ex. Suddenly, I found myself getting incredibly turned on, imagining him doing something naughty that we never did before. It hit me hard, and I couldn't control it. I closed my door, pulled down my pants, and started touching myself right there in the office chair. My hand was working fast over my clit, my breath coming out short and sharp as I imagined us locked away together. Soon enough, I felt that familiar pressure building inside me, tightening up with each stroke. I wanted to scream but kept it in, squeezing my eyes shut, arching off the seat. When I finally came, waves of pleasure washed over me, my back bowing against the chair. It was liberating and terrifying all at once. Am I just crazy for feeling like this? Is it normal to crave these kinds of fantasies so intensely even now that we're apart? What am I supposed to do with all of this?