If you feel as if it was sex, then it was. Nobody can make that decision for you.

As for telling your wife, I agree in that you should just keep it simple and to the point. You could just mention that you'd paid for sex during your college years because you were busy and stressed, and wanted her to know and leave it at that. You'll know if she takes issue with it, and you'll know if she doesn't.

As for western culture (lots of cultures in that group!), it depends on the group of people, the region, and definitely the person. I was surprised to find that I didn't care when my husband told me that he used to work in the industry as a driver and in sex shops. All you can do is be honest and hope for the best.