Your situation is very complicated - I am assuming that you were not on active duty at the time of the party, because otherwise they would be considering court-martialing you. The "general" rule is that the Army will not tolerate people that use drugs such as cocaine. 99% are discharged with "bad paper," i.e., a UOTHC discharge!
Your rank, experience, to include deployments, MOS and how your NCO's feel about you and whether or not any officers will support giving you a "second chance."
What is your unit and where is it located? I routinely handle these kinds of cases and Buffalo is only 85 miles from my office. This is not a secure forum, so do not provide any specifics. Contact me privately and we can discuss some options for you. You MUST be proactive on this otherwise you will most assuredly be looking at a discharge process.