He thanked me for loving him?

I love my boyfriend with all my heart. Sometimes he has anxious moments and needs reassurance and i told him i love him and he said thank you. I asked why he thanked me and he said “for loving me.” It broke my heart for some reason. I dont even know what to say back. He treats me better than I’ve ever been treated and i truly love this man with my whole heart. Anyone had this happen before and what do you say?