I'm cautious of telling somebody what something is, because ultimately it's up to the person who had this experience to decide.

However, you're specifically asking for opinion, and in my opinion, even before I read your line about thinking he was getting off on hurting you, that was my very first thought. As soon as I read that he specifically asked what hurt more and then continued, that was my first thought.

You're not overreacting OP, and it's quite common for people to doubt themselves and convince themselves that they're overreacting. This is part of the thought processes that occurs when somebody crosses boundaries. It's a very confusing experience and many thoughts go through people's heads including rationalisation. It's a coping mechanism. OP, he did cross boundaries. He specifically asked you how it hurts more and continued to do this, even though he knew it hurts you.

I'm sorry you experienced this, OP. It might help to speak to a therapist about it, if it's causing you, or does cause you emotional distress.