Compounding anxiety

I managed to oversleep for my shift yesterday morning. I had set my alarm clock for the time I needed in pm instead of am, and considering I had a short morning shift, it was far too late for me to come in by the time I woke up.

I could have called in, but I was too embarrassed. I left my phone off. I checked my voicemail later on and my boss had called. I tried to hype myself up to call him back. The phone rang, and I became paralyzed with fear. What would I say? I let him leave another voicemail. It is the next day, two hours before my shift, and I still have not called.

Now I have to give him a reason for not only being late, but not calling back. At this point, I am debating calling him back as I leave for work (so that I am walking and it seems less frightening) and saying that I had left my phone at a friend's house. I hate lying, and I hate talking on the phone, but at least he won't see the obvious cues in my face.

I am still so nervous about the prospect. There were times when I missed a class in college and was so freaked out that I didn't go back the next time, or the next time, and ended up dropping out. I am the kind of person that always shows up early for work, because I hate the feeling of being late or missing work - of feeling "bad." Deviations from that norm are always hard to deal with.
There are those voices in my head that say, "You already have one job. This is just another one. You can find another second job. You'll never have to face him again." Which is just entirely unreasonable, and I know it. This is a perfectly good job, and the boss is not a hardass, and as long as I don't screw up again, I will be able to continue working there and this incident, over time, will be forgotten. I do not have the money right now to lose a source of income. I think what vexes me is that I've only been at this job for three weeks, and have not established a positive reputation yet. And therefore, this will cast a pall over me that will take a lot of time to erase. I worry that any other area of deficiency in my performance will take on added weight. There's also the fact that I am unsure about this job in general, and see it as a temporary thing until my first job gives me that full time status. (Should happen in January.) It feels too familiar to my last job, which lasted five years. And it has the same inherent issues for me - multitasking, lots of people contact, expected to be upbeat and sociable the entire time. I am more drained from a four hour shift there than I am from a 6-8 hour shift at my other job.

But I am making excuses, once again. Until I have something else lined up, I need to keep this job. And I need to find something to tell my boss about what happened yesterday and why I panicked and didn't call him back, and I need to march into that store today and work my shift.