No one will answer :(. Please help?

Okay so, I have been with my boyfriend for 2 months. He is amazing, I love him, and sometimes I wonder how I got so lucky as to be with him. But whenever he doesn't talk to me often, I get worried. He doesn't have a cell phone, so we don't text. Instead, we talk on the phone when we have to go lengthy periods of time without seeing each other. Otherwise, we email everyday. Well, I emailed him tonight many hours ago, and he hasn't bothered to email me back. I haven't heard from him since lunchtime today, and I feel both sad and worried. Also, he stayed the night with me last night (no, we don't have sex, we just sleep in the same bed once in a while) and whenever we sleep together, I always feel so sad the next night when he isn't there by my side. It means the world to me. How can I stop feeling so sad, and so worried about him? I know he isn't busy tonight. I am 19 and he is 21 if this makes a difference.