Relationship getting cold: any advice?

I started dating "Adam" 6 months ago. I have been upfront with him, but lately he has just been more and more withdrawn. We used to spend more time together and have (I have been upfront about my high drive), but lately I don't get to see him much (I know we both work and have our own lives, but I haven't spent time or had in a couple months. I've tried talking to him, but can't get a straightforward answer. What should I do?