Hello Matt: Thank you for sharing your story here on PC.
I see this is your first post here. So... welcome to PsychCentral!
I hope you find PC to be of benefit.
I want to say, up front, that what you have suffered absolutely qualifies as abuse. And how you are feeling about your sister is to be expected. In fact, I'd say it's surprising you are able to be as charitable toward her as you are. Yes, you absolutely should avail yourself of the services of a counselor or therapist as soon as possible. This kind of long-term abuse takes a toll on a person's mental health. You are likely to be dealing with the after-effects of this for years to come.
Finding the right counselor or therapist, for you, can sometimes take a bit of effort. (Not every counselor or therapist works well with every client.) So if the first person you see doesn't seem to be a good fit, it's important to try others until you find someone you feel comfortable with. Here are links to 4 articles, from PsychCentral's archives, on the subject of how to find a good therapist:
https://psychcentral.com/blog/how-do...dium=popular17
https://psychcentral.com/lib/how-to-...dium=popular17
https://psychcentral.com/blog/10-way...ood-therapist/
https://psychcentral.com/find-therapist/
Since you're new to PC... there are a couple of other forums here that may be of interest to you. These would include the relationships & communication forum & the teens' lounge (no adults allowed!)
Here are links to these forums:
https://forums.psychcentral.com/rela...communication/
https://forums.psychcentral.com/teens-lounge/
I, of course, don't know how possible it is going to be for you to see a therapist any time soon.
I hope you can. But another thing that can sometimes be quite helpful is journaling. You can write, here on PC, about what you've experienced & how you feel about it. But you can also create your own journal. Here are links to some articles that talk about the benefits of journaling & how to get started:
https://blogs.psychcentral.com/imper...mental-health/
https://psychcentral.com/lib/the-hea...of-journaling/
https://psychcentral.com/blog/techni...your-emotions/
https://psychcentral.com/blog/tips-to-start-journaling/
https://psychcentral.com/blog/4-jour...dium=popular17
https://psychcentral.com/blog/30-mor...dium=popular17
https://blogs.psychcentral.com/weigh...know-yourself/
https://blogs.psychcentral.com/weigh...dium=popular17
My best wishes to you...
