What Am I Doing???

I feel so lost and confused most of my waking hours. I am working at a job that I only tolerate, and am doing little to nothing to improve my current situation. I go to work, smile for 10 hours while inside I am dying, come home, eat dinner and sleep. So why do I stay? I could say that I stay for my co-workers because that would be mostly true. The four ladies that I work with (and even the bosses wife when she isn't reprimanding anyone) are WONDERFUL. They really do make my job worthwhile most of the time. But I am realizing that I am just not that good at what I am currently doing. I am doing a passable job I would say, but I don't think I am great or even fantastic. If this was a grade in Harry Potter I think I would be doing my job at an A level (Acceptable for those non Potter heads). On a good number of days I would probably even give myself and E (exceeds expectations) but NEVER an O (outstanding). And maybe it is because I really don't want to be doing it. But even things that I don't want to do I should be giving 110% because that is just the person I am. So why am I failing to do so many things on my job? Why am I swamped in tasks? And why does no one around me seem to notice? And now, just today I came to the realization that I failed to do something pretty major at work and the consequences of this are going to affect a lot of people, and most importantly could cause a family of patients to lose their trust in us! I have a huge knot in my stomach, and have a feeling that I won't be getting much sleep tonight because now I will have to go into work tomorrow and confess to what has happened, what I have allowed to happen, and I have no solution on how to fix it without our clinic looking really bad. I don't really even know what to say to my boss or my co-workers and I just dread that I could get fired. (Although I wouldn't blame them if they did). Although most of the time I don't feel like this job is where I really belong, I still don't want to be fired. And at the same time, I have a secondary feeling that there is SOME reason why I am still working at this job, despite the fact that I haven't really felt connected to this job from the beginning, because despite my best efforts I can not find a job doing what I really want to do. So here I sit, not knowing which direction I am headed, nor which direction I am supposed to be heading. It is like I am floating in a abyss. And I just want out.