@hufflepufflewiz,
Hon, you need to talk to a trusted adult. This can be a parent, a teacher, the school nurse, your doctor, a member of the clergy if you're religious, an older sibling if they're a grownup - those kinds of people.
Tell them what you said here (copying and pasting your topic is perfectly fine).
In particular, talk to them about how you feel about yourself, okay? Because I know it hurts.
A long time ago (as in, over 40 years ago), I was bullied, too. So I know a lot about what you're going through. I know that it sucks and you feel like everyone is against you.
Telling an adult will start you on the road to getting the bullying to end, and to getting tools for dealing with it.
PS I know you're not horrible. You're a hufflepuff and hufflepuffs are awesome.
We're on your side.