My bf cumming

Okay so my bf I. The beginning use to always want to have sex. Like his sex drive was high. He would cum more than 3 times and still be hard and horny. A year later he doesn’t want sex a lot because he said he has to have time to “build it back up”. He goes soft after the first cum. What do u all think it is? When I asked him he said his sex drive isn’t as high as it use to be and idk. Sex is so different. He use to want to have sex a lot and sometimes he gets mad that I ask but he said he gets embarrassed when it goes soft after a few minutes but he didn’t do that in the beginning? ( we had lotssssss of sex in the beginning ) thoughts? Also I’m 20 and hes 23