I can remember your being here before over an eating disorder - congratulations for getting it under control, a big thing. I also remember you giving very good advice to Taylia (Guest_201). I'm not sure it is much good me talking about the resources that are open to you as? I'm sure you know them. From councilors to doctors.
May I ask if you have medical support at the moment?
What I would like to talk abut is about expectations, both other people's and yours. While you do have a high persona goal (Veterinary Science Honours, ATAR 99) mostly I feel you are frightened not meeting others' expectations. A's in everything, a school award, and so on. You give reasons for this, telling your parents about your results plus your friends. You go further and worry that you will not be regarded as intelligent as your sister.
One of the hard thngs to do is set realistic goals. To be loved and cherished is as important as going to uni, and so I'd suggest you could consider telling your parents exactly how you feel, the level of attainment you feel confident you can do without going to excess, and see what they say.
Of your parents whom do you think might be most approachable?
Do you think this is something you could do?
I do hope you came back and talk more, even if you disagree that should be no bar to returning and pointing out flaws, or that is impractical