First off - tell you gf what you are going through.
Secondly - if you wake up feeling the same way you call 911 (here) or an ambulance, not the hospital. You tell them that you are having suicidal thoughts and have a plan. Thinking of taking all the meds at one time or stabbing yourself in the heart with a sword are both plans.
Remember, right now you are not thinking clearly and you are not in control of your feelings. Coming off all the medications at once can cause withdrawals and cause lots of mixed feelings mostly paranoia and anxiety.
If your girlfriend leaves you, she probably would have eventually, if she loves you she will help you, but you have to be honest with her. If she has no clue, she will feel worthless and leave.
If you loose the job, there will be others.
If you end it all - there will be no more love, no more gf, no more jobs, no more laugther, no more sunshine, nothing.
I know what you are going through, I too, have wanted to end it all, however, "all" was the disease and the symptoms - not life.
Please reach out and talk to someone.