I need good sex!

Why can I never be satisfied with having sex with my boyfriend? I love our relationship and everything else is perfect except the sex. I want a girl fwb. He has given me the option before but I turned it down because I could tell he was upset about it. I need the sex. I need all of it. Our sex life is not passionate or exciting to me or how I want it. I've tried asking him to do more but his sex drive is so low that he isn't interested 😓 I'm gonna burst!!! Has anyone done this before?