So, basically, you used illegal drugs while on probation, got caught, and decided you had better things to do than deal with the consequences? And now, after four years, it's caught up with you?

You're correct to be working with a lawyer. Ideally you'll be able to convince the court that you've grown a lot in the past four years, regret your actions, and... well, deserve (as in 'deserve a break') isn't the right word, but that the court should give you another chance.