My grades at school have gone right down and I'm bunking off when my mum's at work because I can't face all the lessons I have with the bullies. I'm being called names about my weight and I have nobody to go around with at break. When I sit down with my packed lunch the others get up and move away. I'm taking so much time off that my mum is going to find out soon. I've told my head of year and she spoke to them but they're still doing it. This is making me feel very depressed and I've self harmed a few times.
I can understand why you don't want to go to school but if you take time off then you're damaging your chances of doing well in exams and that might affect your future.
Your mum needs to know what's going on so that she can help to get this sorted out. Try to find a time when she isn't busy to tell her or if you can't do that have a word with a grandparent or another member of your family or close friend and ask them to help you explain what's going on.
As you've already told your head of year then your mum needs to write to the head teacher explaining what's been going on and asking what strategy he/she can introduce to deal with the problem.
Bullying can make you feel very upset and depressed so if you feel like that see if your mum thinks you need to see your doctor. Please don't try to lose weight just because the bullies are calling you names. Only your doctor should decide if you need to do that, you could make yourself ill if you diet without medical supervision. Your doctor might be prepared to write a letter to the school if the stress from bullying is making you ill.
Self harming is very dangerous and can easily go wrong. Please talk your feelings over with your doctor because he/she will be able to help you.
Keep a diary of who does and says what because that can be useful for the school to see what's going on.