My job is driving me crazy?

I'm a bank teller. I took up this job as a high school graduate looking for his first job. I figured I wouldnt like it, but I tried it anyway.I'm 5 months in, and I've never been so close to the brink of quitting.

I'm not really a people-person. I don't smile much, and I'm a but socially awkward. I prefer working in isolation that interfacing with people all day. I hate that at times the line is so long and I have to use the bathroom. It's very boring and very stressful.

Here's the biggest issue, we at times have to work overtime and we don't get paid for it. We have to do more work than we ought to. At times, we're tending to customers all day, yet cheques are forced on us to enter onto the system. Where should we find the time?

My job is giving me nightmares. I hate my job but I dream about my job. It's insane. It feels like even when I'm off work, I'm at work, because I just feel like it's hanging over me. My mental state is on the decline. I'm depressed, I'm unhappy and stressed. Everyday, I dread going there. Same thing over and over. Just as you think you'll finally have a good day, everything comes crashing down. I sometimes have to cancel plans I have of going to the gym because I have to stay back at work. Even on less stressful days, I'm just not stimulated. The money is sufficient but it isn't worth the twist it's putting my mind into. I don't know what to do.