Run of the mill sex

Help. My boyfriend is 7 years older than me and is obviously way more experienced in bed than I am. He doesn’t like plain sex (missionary, hitting it from the back) it doesn’t get him off... AT ALL. He won’t tell me what he likes because he doesn’t want to make me feel like I HAVE to do it. All he has said is he likes nasty, and sometimes a finger in the ass. I need ideas of what to do to spice it up and make him cum... it’s putting a strain on us.