Confusing anxiety

Hello! So this post isn't actually about me, it's about my boyfriend. So beginning of our relationship Is used to get very nervous around him (to the point of feeling sick), up until a certain point. We have now been dating for a whole year, and the tables have turned. The last two times I've come to him house he has gotten so anxious he has thrown up. We've talked about it multiple times, and he doesn't know why it happens to him, because it never did before. It almost seems to get progressively worse. Has anyone else experienced this or have any advice at all? Thanks~!