Boyfriend acts like a child sexually

This issue only arose in the past year or so. My boyfriend acts like a 9th grader when it comes to anything sexual. We used to have great sex, I haf a pretty insatiable sexual appetite when we started dating and he fufilled it awesomely. In the past year or so though he acts like he doesn't know how sex works, doesn't want to try anything adventerous and I'll honestly be lucky if we do it more than twice a month (we used to up to three times a day) when i try to be cute and subtly show him what i want, he literally uses baby talk with me which is a huge turn off. Everything i do "tickles" or makes him feel uncomfortable. It literally makes me feel like im doing something wrong like i feel like I'm violating a child when im reqlly just trying to have some fun with my ADULT boyfriend in bed. Its a huge turn off and i dont know what to do at this point.