I'm actually going through something kind of similar right now. It's a scary thing to feel dependent on someone, especially if there's always the fear that they're going to leave. I know it's hard to keep your thoughts separate from your emotions, but try not to just distract yourself. Sometimes distracting yourself temporarily can make anxiety worse, because you're not addressing the actual issue.
If I were you, I'd vent about this to someone who can remind you of all the reasons your boyfriend loves you. It might make you feel more vulnerable to tell him exactly how panicky you've been feeling, but sometimes getting all of it out verbally (to a therapist, a friend, or a family member?) can help you realize that not much of what you're afraid of is legitimate.
I totally understand the feeling of loneliness too. I live in a city where I don't know a lot of people (other than my boyfriend), and when he can't hang out with me or talk to me, I often feel like I'm grasping at straws to find someone else to relate to and spend time with. Building a real friendship with another person will balance you out, though. Take baby steps.
Also, I'm practicing ignoring my negative thoughts about my boyfriend, which might be useful to you too. I feel myself starting to analyze a situation, almost like it's a thought I can't control, and I tell myself, "no, we love each other, I'm not going down that road because it's doesn't make feel good." You are not your emotions, and your fears are a passing thing.
Also, you're not alone!