Boyfriend doesn’t want to have sex anymore

my boyfriend and i have been together for almost 2 years, we moved in together about 6 months ago. recently within the past month or 2 he never wants to have sex anymore. the last time we had sex was terrible it lasted 5 damn minutes which is so unusual for him. i feel so unwanted, i’ve tried to talk to him about it but that never works. mind you he is 20 & i’m 19. what is wrong with me😭