This has happened quite a few times over the course of our two year relationship, most recently this evening. I wouldn’t say I’m below average intelligence, equally not the sharpest tool by any means 
Each time he had corrected me I’ve brushed it off and thought ‘oh well at least I know for future’. Tonight it hit a nerve for some reason. I mispronounced a word during dinner, a fairly commonly used word, fair enough I said it wrong. However he understood what I had said, so it didn’t affect the conversation in any way, but he repeated the word back to me correctly afterwards which made me lose my train of thought for the conversation, which inwardly pissed me off. I didn’t say anything as we were out and I wanted to enjoy my meal but I was noticeably quieter afterwards.
It doesn’t happen often, maybe once every couple of months or so. It is quite possible that I’m being over sensitive about it, as I’m sure he doesn’t mean it maliciously and just wants me to not sound like an idiot.
I kind of wish I could think of something quick-witted to say back to him when he does this but I tend to feel too defensive.