How to stop the "distant" feeling in my relationship?

I'm aware that the honey moon phase doesn't last forever, I just feel like my boyfriend stopped doing the things it took to get me. Yes, I do nag and tell him to try to be more affectionate & he does get frustrated, saying I should already know he loves me or he wouldn't be with me. We've been together for one year 1/2. I still write him sweet things, buy him stuff I know he wants, surprise him with it.. When we are with each other, I know he's next to me but at the same time I feel so distant. Like everything is a routine.. I'm scared of falling out of love. Should I just start being less available?