boyfriend seems disinterested 18+

So my boyfriend and I have been dating for a little over a year and a half and our sex life has been the same since we started dating. we have sex a lot but it's just short and to the point. It's not intamate, it's boring and it's not fun. It makes me feel like I'm not pleasing him, he doesn't like doing positions we use to, it's just boring now. he won't pull my hair he won't spank me, talk dirty or anything. it's pretty much missionary or me on my stomach. i dont know what to do, he won't experiment with me to try different stuff. Is it me or is he not in to me anymore..? i dont know what to do...