After four years together, my fiance is still embarrassed by his tourettes around me... What to do?

Okay, well, I have a question regarding my fiance, James. We met in sort of a strange way; I met him through a friend who brought me to a party at him and his roommate’s place. My friend ended up getting drunk and fell asleep in their living room. James and I don’t really drink much, and somehow we started talking. We spent 4 hours talking in his room after the party was over, and I really liked him. He’s so sweet, and kind, and understanding. It was really late, and somehow we started getting a little touchy; things escalated, and we actually ended up having sex (which is crazy, because I’m not that kind of girl at all. I had only had sex once before with my boyfriend of 6 months). I slept at his place that night, and since then, we’ve been inseparable (We were 21 then, we’re 25 now and we live together, as well). We just got engaged a couple of weeks ago, too. :)

Anyways, James has mild tourettes as well (It’s nothing big; his hands will twitch sometimes, and he’ll occasionally furrow his brows or roll his eyes, etc. You have to really pay attention to notice it), but it gets more frequent when he’s nervous or stressed. Otherwise, it’s nothing ground-breaking; a slight tic every now and then. However, even after 4 years together, he still seems to act funny about it sometimes. He knows that I don’t care that he has tourettes; I rarely even notice anymore. However, there’s certain times where he seems embarrassed about it. If he has a tic (sorry to be blunt) while we’re having sex, he looks almost ashamed, and he’ll stare off for a bit before he’ll look at me again. Sometimes if we’re cuddling, his hand will twitch or something, and he’ll get quiet and look away, or sometimes he’ll even apologize for it. Every time he does, I tell him, “James, I don’t care, it’s fine. Don’t apologize, love.” His tics are just like another part of who he is, and I love everything about him.

The other night, we were laying in bed going to sleep, and I had my head on his chest, and his arms were around me. His hand kept twitching, and he apologized, saying “I’m sorry, that must be really irritating for you.” I don’t know how to get him to realize that his tics don’t bother me? It doesn’t matter to me; he’s the same person to me, whether he has tourettes or not. What should I do? Why is it that after 4 years together, and 2 years of living together, he still seems embarrassed by it? I feel terrible that he’s embarrassed by his tics when really, it doesn’t matter to me one way or the other. Advice?