My boyfriend doesn’t want to have sex

Hi, me and my boyfriend have been going out for almost a year now and have been living together 5 months, at the beginning of our relationship, we were having plenty of sex, multiple times a week, and now, we are barely having it once a week, its like he doesn’t want to or something.. He leads me on, but as soon as he gets in bed, he falls asleep.. Or he gives me a bunch of excuses like he’s too tired, or he’s busy watching his Netflix show or gaming.. I’m getting worried there is something going on with our relationship or with me.. Is it normal for a guy that’s 21 years old to not want sex like this??