i need to come clean

there's literally no way around it. i assaulted her. when my sister (21f) and i (23f) were both kids (maybe her 6 and me 8?) i came across inappropriate things online while browsing on Instagram. at first it was one post, but then it was all that i ever thought about and looked at. i took it upon myself to ask her to do those same things with me. this might have happened a few times, but i can't remember clearly. the only memory i have of it was when we were both under the blankets. but without a doubt, it happened, and now i feel it's time for me to come clean to my mother about it.

fast forward to now, and she's been having multiple mental breakdowns. today i heard her on the phone (?) with someone screaming, and afterwards she started screaming about how much she hated me. just a couple weeks ago she called the police to report abuse. i think she might be talking to people online about it, who now are telling her that she's unsafe at home. it's so clear that it's what's been keeping us from ever being close.

in the time since, we've both been given psychiatric medications, but that can only do so much when the root of the problem isn't solved. all of these mental breaks from my sister and i over the years have been stressing our mother out so horribly. she isn't the same person anymore. what's worse is that she's unaware of what i had her do to this day. every time i think about my younger self i feel disgusted and sick, and for years I've been thinking of ending my life. i feel like I've failed as a sister, even if i was a kid at the time, by actions are inexcusable. i don't know when or how to tell my mother. the only thing i know is that i need to be the one to do it, because i was the one that caused the abuse, not her. so the least i can do is take initiative. i really need help, because this is weighing on us so heavily and the more time passes, the less "committing" feels like just an idea. for either of us.