arousal

so, my boyfriend and i have been together for almost 4 years so were 100% comfortable around each other. Within the past 6 months or so, ive noticed that im going dry during sex. this makes it extremely uncomfortable both physically and mentally because he thinks he is not turning me on anymore. i think my sex drive is higher than ever and i still cum even though im constantly going dry. i have no idea what it could be from or how to fix it. anything would be helpful!!!