I took 18 5mg hydrocodone in a 2 day period will they be out of my system in 6 days?

Probably: They should be out by around 5 days.

Maybe Not: Drug clearance from your body may be very difficult to predict. Factors involved include the varying types, amounts and combination of drugs ingested, their individual elimination half-lives and any co-existing medical problems (liver or kidney issues that can slow down elimination). The amount of hydrocodone involved here suggests you already have a pain management md helping you. Do check in!