Insecure bf

Hi, so me and my bf have been together for a year and a half now and he’s always been a bit insecure about how he looks but recently it got loads worse. I find it really hard to help because I think he’s perfect in every way so I can’t understand his insecurities but last night he told me that he never believes what I say about him and it kind of upset me. Any tips about the whole situation?