Great advice abovr but it does concern me about the doctors.
Teachers can be good for this. I remember being really ill at college and my mum wouldn't let me stay off and one of my teachers who had questioned why I was there said I could come in as normal and they would find somewhere I could rest and get better.
Do you have a school nurse who could help? A PE teacher could be a good choice as it's a suitable excuse that they could have picked it up as infectious to others in swimming or barefoot PE and could maybe write a note to your mother or help in some way?
How old are you? I am guessing under 15 so you can't take him but another relative is possible as above.
You could also check if there is a walk in centre near you which is easier to go to without making appointments and such.
http://www.nhs.uk/AboutNHSservices/walkincentr es/Pages/Walk-incentresFAQ.aspx#q06