phatass
Bluelighter
you might miss a few breaths, but you won't die from forgeting to breathe, ev en though cns depressants make your breathing more shallow, at that sort of dose ull be fine 
I've had the same thing happen to me mostly when I smoke bud and maybe a once or twice on opiates.
^I was making this point as well. It sounds like the OP is tolerant to all three classes of depressants (opiates included).
However, it should be stressed indeed. Without tolerance to these drugs, combining depressants and opiates is a very dangerous gamble.