It is likely that you are suffering from really severe anxiety.For any number of reasons, which it sounds as though you have had a really really rough month or two here. If you are as you say going to be "at my hearing by myself" in other words, you don't have a lawyer now, it would be greatly to your advantage to have a lawyer. But then, if as you say, you lost your good job due to the circumstances in the world lately, financial strains may be a huge issue. And you mention you've had a break up with a girlfriend, heart issues, probably due to stress and some dental work which involved pain meds. It sounds as though these things showed up in your drug testing?
Flatly, the best possible thing you can do for yourself right now? Meetings. On-line meetings, virtual meetings, something to get control of what the court is going to be inclined to perceive as an alcohol and possibly poly-drug addictive pattern. And in these time, frankly, they're NOT wanting to throw the book at non violent offenders and simply lock them up right now, since that almost guarantees they are unproductive, no job, no homelife, no hope of doing better in the near future. And a possibility that you'd be put in a very dangerous situation regarding the current COVID-19 situation.
What they want very much to see is somebody who is doing better, is very very sorry and is never going to do this (whatever it was) again. no excuses for what has happened, no funky stories. The more you can look like that person when you do finally get to court, the better it is for you. It sounds as though you have done some things right, as in completing all your classes, paying all your fines, etc. I'm sure that was contingent on your good job which you were holding on to. but have now lost.
Do not let your life go completely to hell just because some other things have happened that have caused you some severe set backs. Find some rehab meetings on line if nothing else, in person if possible, but somewhere, get hold of yourself. Though you've had some slipsies, and too many failures and watered tests and such and they're revoking your pre-trial diversion, that just sort of means it will be considered when this other business comes up.
But instead of sitting around waiting and looking at the laws and thinking about how worst case scenarios they COULD, if they so choose, do this to you, sentence you to this or that or whatever, be thinking of how you can proactively get yourself into a shape where you can come out of this if you are given leniency. Be ready to talk about what you have done while unemployed to help yourself, work on your total recovery from possible alcohol/pill, whatever dependency. It is inherent to people who have substance abuse issues that they do have a tremendously high level of anxiety. It's natural. You need help dealing with this, regardless of what happens when you do go to court.
It would be a good thing when you are in court if you don't throw yourself into a much detailed story about how you happened to be stopped with those two open beer cans. It doesn't pass the sniff test very well, regardless of how innocent it may have been. Just be ready to talk about how you're very sorry that all of this has happened, and how you are moving forward to do a lot of things differently in the future. That always works better in court than "I was framed, I forgot to check the car to see if there were empty beer cans in it, no one understands the stress I'm under, I'm having a hard time, water from the tap jumped into my urine samples, etc. " Those sort of stories never work well.
Good luck to you, these really are hard times for everyone and you are having to deal with a lot of uncertainly on many fronts.