How to help my boyfriend be more confident?

My boyfriend and I have been together for about 2 years now and we’re both 17. I talk a lot and make friends really easily, whereas he is on the quieter side. He likes to draw and paint, and he loves jiujitsu. Recently he made a comment about how he sometimes feels insecure around me in groups. He laughed it off, but I’ve been noticing it a lot more since then. He doesn’t hold my hand around anyone, he stays quiet in groups when I’m there, and he fidgets a lot whenever I talk. He’s kind and funny and handsome and he has nothing to worry about at all. I’m worried I’m making him feel bad? Is there any way I can help him to feel less insecure or do I just have to let him grow out of it? I never make fun of him or anything like that so I’m not sure if it’s my doing or something else.