Sex drive. ADVICE NEEDED

My boyfriend and I have been together for a little over a year now. We moved in together about three months ago. He is works 6-7 days a week and I am currently off work for the summer. (I am a teacher) I often find myself wanting to have sex and he is not interested. Often using the excuse he is to tired from working all the time. He also says he is soon to be 30 and not as interested in sex as much as I am because I’m 5 years younger. Because of his low desirability in sex I often find myself questioning if it is something wrong with me or maybe he just isn’t attracted to me. What should I do?!? Is this normal?!?