I HATE SEX

i’ve been dating the same guy for 3 years now.. we’ve always been sexually active and passionate about it. i used to LOVE sex and we would do it a lot. we are doing long distance, i’ve never had sex with anyone but him but somehow i dont feel like having sex as we used to.. i just dont enjoy it as before. he gets really sad and worried and i just really want to know if it’s normal to not desire sex at all and to be ok without having it for days. he thinks i don’t like him anymore but i do love him, i just don’t feel like having sex AT ALL or any sexual activity....its this normal? has this happened to any of you? HELP!