My Whole Relationship Is A Lie💔

I’ve been w my bf for 6 months. I’m 15 & he is 17. His parents don’t know about me. Every time he goes out w me he lies to his parents about where he is going. I just found out that he told his friends I’m 16. He says if I come to his prom that if anyone asks i have to tell them I’m 16 and in grade 11 when I’m 15 in grade 10. Him saying these lies to the people he is closest with scares me. Why is he so okay with lying? Our whole relationship is based on lies. I like him so so much. What should I do?:(