Hey there Bella. I am proud of you for reaching out for some help and I want you to know that none of this is your fault. Abuse in any form is hard to deal with and when it comes from a parent, who is supposed to love and protect you, it's even harder.
Three years is a long time to have dealt with this already. I think the best thing you can do for yourself is to reach out and ask for some help. Talk with a teacher or a school counselor or even your mom if you think she will listen and help out. You don't deserve to be put through this. No one has the right to abuse you.
If you live in the US, you could also contact social services for help. The have a completely anonymous reporting system set up. This way someone will have to look into it, but you can't get in trouble for making the report.
As for the flashbacks and memories, I know those are really hard, but they can be overcome. Counseling is definitely something that can help you work through them. I truly believe it helps to talk about what we've been through and a therapist can help you find healthy ways to cope. Some things I have found that help are different grounding exercises. I have been taught a few so if you're interested in them, feel free to
PM me and I can explain the ones I've used.
I hope you're doing okay right now. Keep yourself safe.
<3 Emily