Unfortunately, as Kittycat5 said, tif 6mhis is an inherently dangerous combination. Just judging by the way you describe your usage of depressants, it sounds like you probably don't have a lot of self-control. I'm not trying to do the right vs. wrong, ethical thing right now. I'm simply trying to give you the most effective advice I can.
If you're taking "A LOT" of Oxycodone, it would not be surprising if 6mg Lorazepam (Ativan) killed you or got you a trip to the hospital. The issue with Benzodiazepines and self-control is that if you're already lacking self-control, taking the pills will remover any semblance of self-control. Sure, this can be funny, but losing control can also lead to catastrophe. You could drive a car, get robbed, spend all of your money etc.
I would really just not take the Benzodiazepines, but if you do, I would strongly advise against exceeding a dosage of .5mg - 1mg Lorazepam. If you're already taking other CNS depressants, that could easily be enough to "get you where you want to be".
Please be careful. Be responsible and really think about what you're after and the potential consequences before making any decisions.