My stepsister (20F) and I (24M) have never gotten along. Her mom and my dad got married when we were six and ten so we’ve known each other for a long time. In my stepmom’s eyes, she could do no wrong and anything bad that happened was pinned on me. My dad is a complete pushover so he would always fall over to whatever my stepmom would say.

When I was about 15, I started gaining weight. My gf broke up with me (woohoo high school romance), I started failing some of my classes, and I quit baseball. I started to stress-eat and ballooned up from 125 pounds to 162. I guess at that point she decided she was “cooler” than I was and started mocking me and making fun of me, calling me names like “fatass” and “chubster”. I would constantly go to my stepmom about it and she would tell me she’s just teasing, she’s so much younger, why are you getting upset?
I got pissed off to the point where I just started avoiding her and locking myself upstairs in my room with a bag of chips.
At 22 I hit 270 pounds and I knew I had gone too far. I was way past my weight limit and bordering on obese. So as a New Year’s resolution, I decided to start losing weight. I cut out all junk food and started hitting the gym. Around this time my stepsister started to overeat too, I don’t really know why but she gained over 30 pounds. She still was constantly belittling me about my weight (which admittedly, was way over hers).

By the end of this year, I lost 120 lbs. It felt amazing. My stepsister now weighed more than me. Over Christmas dinner, all the aunts and uncles and cousins were complimenting me on my weight loss, telling me how I looked so much better. My stepsister just sat there smoldering. Every time someone said something she’d add, “He’s still pretty big”, “Well he didn’t get rid of that face roundness”, “Maybe lose a little more around that gut”. It was infuriating and I was getting angrier.

Now here’s where I might be TA. Finally, at her last little snide, “Look, you know you’ll just put it all back on. Why do you even bother?” I flipped out. I yelled, “Why can’t you just be happy for me, instead of getting on me for every little thing?”
She said back to me, “Defensive much?”
“Oh, I’m sorry. Did I hurt your 200-pound feelings?” I asked her. I probably should have stopped there but I kept going. “Calling me a fatass. Look at your plate! You’ve eaten half the table, fatty!”
She started crying and left the table. My stepmom screamed at me, saying just because I was insecure I can’t take it out on everyone. I said, “Oh, so *now* you’re talking. Not in the past ten years of constant ‘fatty’ and ‘lardass’ and ‘porker’!”
“But you’re way older!” she whined.

I left the table too and went home. I woke up today to a thousand messages from my stepmom, my dad, and my stepsister. They were saying I wasn’t welcome to their house until I apologized. I’m not going to.

AITA?