You can't breathe.... You feel lightheaded when you front squat? If that's the case it's b/c you're choking yourself with the bar. You want it to sit on your clavicles. Now the bar is up tight against your throat and if you're not careful you can actually pass out with the bar sitting there if it's to close to your throat. I've gotten light headed and almost dropped b/c I was basically giving myself a blunt choke (bar pushing against my throat).
It's a fine line between having it sit just right and the bar choking your ass out, lol. Finding that line will come with time.
You shouldn't breathe while you're performing the lift. You take in a big breath, pick up the bar, get set, take another breath, arch the shit out of your back, arch some more, and than perform the lift. Don't breathe out till you're coming back up out of the hole.