My BF and I sometimes have these really ephemeral and transcendent moments when I feel fulfilled and placid. But then he doesn't call me and I'm so over it. Sometimes he crushes on my BFF! I also have severe commitment issues. Also I think I may have extreme catagelophobia, so don't make fun of me!
It's hard to tell exactly what's going on from such a short question, but here's my best guess. You've associated people with some type of painful or worrisome experience. Maybe you fear that they'll ridicule you, subordinate you, reject you, make you feel lost, sad -- whatever. The particulars don't matter, nor do you have to know where it all started. The point is, you've got this automatic association that makes you worried even when the situation is actually safe. I assume it's a pretty prevalent theme in your relationships that makes you appear sensitive to others.
When your BF hasn't called in a while, your worrying grows and you get more and more agitated, vulnerable, and uncomfortable. You premeptively reject him by shutting off your feelings and being "over him." You're numbing yourself to the discomfort and vulnerability and at the same time, reducing your dependency on him. Less investment = less risk = less worrying. When you avoid commitment, you similarly reduce your dependency on him. It's analogous to driving a car with insurance: even if you fuck up, you have a backup, so you're not so worried.
You say he's crushing on your BFF. Are you reading into it? Is it a serious danger or just some flippant remark he makes? If it's the latter, suggest he build a shrine on a lake and dedicate it to her, or maybe cut off his ear and email it to her -- better yet, cut off yours so you don't have to hear him tirelessly fawning over her. Use some humor; he'll get the drift.
Good relationships are built on trust. Not just trust that he won't cheat, but trust that you can have flaws and still be okay. The transcendent moments might come and go, but the value comes out of the friendship and dialogue which is sometimes trivial, sometimes silly, sometimes interesting. But transcendence is not the norm. I don't even think I'd want something like that.The transcendent moments you share might be real, but I would ask you to consider whether they're just others ways you've found to numb yourself to the background discomfort and apprehension.
If my analysis rings true, then start addressing the automatic associations you've inherited that are making you uncomfortable. Don't beat yourself up for it, but pay attention to it. Watch your automatic associations with your BF. When your BF doesn't call, what kinds of thoughts run through your head? What kinds of feelings? Get familiar with it. You don't have to stop it, just get familiar. Example: images of him not being interested or feelings of being forgotten and alone. You can watch your automatic associations with your friends, family, and coworkers. If you've taken something too personally or misinterpreted something they've said for the worst, make a note of it for next time. Example: someone says they didn't like some food you made you take offense to it. You examine it and see that it wasn't personal and make a note of it.
Resist the impulse to "shut off." Try talking instead. If this is just your fear hijacking your perception and making you misinterpret what's happening, then just sit back, notice how "off" you feel and wait for the feeling to dissolve on its own (5-15 minutes). You can even have a little laugh at the whole experience. You could also ponder taking a stand against your fear and telling it to fuck off. I think this'll happen naturally over time.
As you contemplate and practice this stuff, your fear will start to play less of a role in your relationships. If you still feel disconnected from him, or like you're hoping and forcing this to be something it's not, you'll know that it's not just you freaking out but that he's just not the right guy for you.