Hmmm advice maybe??

Me & my SO have been together four years so far, he has been with one other person, as have I. They only slept together twice & had just normal sex. Nothing fancy, no foreplay. So anyway, ever since we've been together he's only been downtown a handful of times.. Unfortunately, I can't get off from just having sex. I really want foreplay. I am more than happy to give him a BJ. I just don't know what to do, he is very plain & boring in the bedroom. I need to spice things up, cause I'm losing interest. He is the best man in this world, I am absolutely in love with him. But I do believe that sex can ruin a relationship. Help! What would you do? What do I do? Uh 😕