My boyfriend doesn’t like to have sex anymore

Hello, my boyfriend and I are 22 we live together and been dating for a year and a half now. In the beginning of the relationship we had sex non stop. Ever since we moved in together I have to basically beg for it and even then we probably will not have sex. We probably have sex 2 or 3 times a month. Has anyone else experienced this and what did you do to grab his attention and get him excited to have sex? My body still looks how it did when we first met. I’m just confused on why all of a sudden we stopped having interest. Any tips on how to work past this? Thank you!