How do I become more confident after long-term sibling abuse?

I've always been picked on because I am the youngest and weakest in my family. My half sister, who was sexually abused by her father when she was three, has always been very controlling and emotionally abusive to me. When I was younger, she would threaten to hit me, say things like "I'll shove your head into the wall" in a really loud voice, and constantly down me. She made it very clear she did not like me because she had to deal with a new family. Now, at 20 years old (and my sister at 27) whenever I try to make decisions for myself with school or what I plan to do in life, she has to step in and try to control me. Nothing I ever do is good enough and she always manipulates me to change my mind. Her logic is literally, "if i couldn't do it then neither can you!" She still acts like a child! I can NEVER stick up for myself without her screaming at me and getting very angry, and of course, its always my fault. It's like walking on eggshells around her. Any little thing will set her off into a rage. And all the while my mom does nothing, and though my dad lives with us, he is barely a part of our lives. My mom has many issues of her own and always ignores problems and never addresses them. She never was there to help me when I was younger, and now she says i'm old enough and everything that happens is between me and her. Again- completely avoiding the situation per usual. Im also always getting yelled at by my dad as well to do things around the house. He has never showed interest in my life- whether it be I got straight A's throughout school or even something as serious as getting diagnosed with an autoimmune disease. Whenever he actually DOES talk to me, he honestly just orders me around.

Now I understand there is far worse out there, but I know this wasn't just "sibling rivalry" either because i can see the effects it has had on me. I am very timid, quiet, isolated and always afraid to speak up for myself. Nothing I ever do is good enough for my standards. I have low self confidence and tons of anxiety, and my mother's avoidant personality has unfortunately rubbed off on me. I have tons of built up anger inside me that I am never able to express. I have gotten myself into many abusive relationships with past boyfriends that have mirrored my sister's manipulative and controlling personality.

So my question is, without going to a psychologist (I've been to so many already and i don't want to waste the money again) with these circumstances, how can I become stronger, more confident and stick up for myself? Moving out is not an option at this point because of school and that would just be avoiding things anyway.

1. tell yourself many times every day that you are better than your siblings and believe it, until you believe in yourself you will never be confident

2. learn to walk away from them , whenever they start, refuse to listen and take yourself to a different place.

3. you are not your sister, you CAN do things which she can't, she is jealous of you which is why she tries to hold you back, do not let her

4. focus on your future, make a plan of what you want to do external to the family stuff and stick to it.

5. remember you are an adult, so you are your own boss not your family.

6. work hard, save harder and when the time is right get the h out of there

7. do not get into discussions with your family about your plans, all they need to know is whether you will be home for supper/bed or not. the rest of your life is up to you. hey at 20 I was living 200 miles away from home looking after another persons baby, my family knew nothing about what i was thinking or doing apart from where i was and when i would next be phoning them!

8. a few phrases to practice are:

I can and i will
just because you couldn't doesn't mean i can't
I'm not listening
no
do it yourself
there is nothing to discuss i am doing it anyway!