Hey guys... as you can see I'm new here. I really need some advice from people who understand how bad anxiety can be!

So I called in sick on Saturday because i had an ankle problem, and was told to get a medical certificate. I couldn't walk so basically I had to wait for my mum to pick me up from campus and take me home (3 hours away) so I could see my GP (who has dealt with this injury before). I couldn't get a certificate til Wednesday and because doctors can't backdate them it only says Wednesday. i was anxious enough as it was about that, and about having to explain that to my boss who hates me. Then my next shift was a Thursday (the day after) and my ankle still wasn't better so I called in sick again. She asked for another doctors certificate, but by this point I was back on campus and couldn't get myself to a doctor. So now I only have one certificate dated for the wednesday, to cover the two days I was unable to work.
I'm so unbelievably nervous about having to explain that to them because I'm scared that they'll get angry and humiliate me in front of everyone, and I don't think I can handle that because I have been really fragile mentally lately. Any advice on how to reduce the anxiety/what to do/how to deal with the impending conflict??