This happened to me with my now ex-husband. And it went on for many years. I was so conditioned to it, I was afraid to turn my back or bend over while doing chores in his presence. I think he thought it was cute, or funny, or somehow twistedly romantic. I did finally put a stop to it, and can remember the rather angry/upset discussion I had with him about what he was doing.

Your husband needs to understand that this is inappropriate and even abusive behavior. No, you're not a prude!