bad day!

I've had one of my worse days on the job today. You see last week I messed up and left the narc box unsecured for a couple minutes and another nurse found it. I work in a jail so security is really important. I did'nt think she would, but she reported it and when confronted, I admitted what happened and thought I did a good job giving the circumstances (it was very busy, the phone rang, I was only a few feet away and nobody else was in the area, ect). Anyway, I knew I'd get a verbal warning, which I did last week. Well today I got called into the bosses office and got a final written warning, skipping the verbal and first written warning. If something like this happens again, I'll get fired. I then felt very discourged even though they said I am doing very good otherwise and have'nt been written up before. Most of the other nurses have been written up several times, but have'nt gotten the final one yet. Anyway, now I've very paranoid and worried if and when I do quit this will be on my record. To make matters worse, I could have made a couple med errors today. Though not major, the one the patient took the meds and then said that it was'nt the right ones. I'm not really sure if I gave him the right ones or not, but its too late to know for sure as he already took them. An experienced nurse said its better to not say you did if your not sure and he should know what his meds are and not take them if hes not sure. Anyway, I'm usually a pretty honest person, but in a situation like this I don't want to admit to something if I'm not sure. btw, the meds he "could" have taken would not hurt this particular patient. My stomach's been bothering me lately too as I think the stress of this job and my other jobs and finances are starting to get to me and I have'nt been sleeping well and that was before today. I just recently started thinking about going back to school again or getting a new job, but I am catching on at this one, but not sure if its worth it. Any comments?