AITA for getting step-sister pregnant?

A little background before I get into it at the time I was 18m and my step-sister was 23f in college.

Around March 2018 my parents got divorced, because my mom was caught in bed with a couple of guys. My dad ended up getting custody of me and my brother. We moved to my dads old town in south east missouri. My dad bought a nice place, and things were going great, other than not having my mom around and school. My brother and I were having a hard time fitting in. My birthday was on September during my senior of high school and it was rough not having any friends to celebrate with. My brother who was a couple of years younger than me was constantly getting teased.

A couple of months into the school year, my dad told us had been dating a women for a while ever since mom and him have broken up. We eventually met her. Her name was Mallory, she was awesome, and couple of years back she also got out of a toxic relationship. She this warm motherly presence that attracted us to her. As the relationship with her and my dad got more serious and deep, we got the chance to meet her kids. She had girl her name was Jamey (the oldest) and a boy named Derrick (who was my brothers age). They were awesome to be around and my loneliness seemed to be fading away as the days went on with them. Then the day cam where my dad dropped on one knee and propose on January 2019. Then late February 2019 the wedding. All of us moved in together and as the months went on it was great, and especially when I graduated.

Once I graduates I wasn’t sure of what to do in life. I never had a job and wasn’t really interested in anything other than playing video games and reading books. I had a lot of time and was bored A LOT. My dad consisted of waking up, youtube, gaming, jerking off, gaming and then sleeping from May – Late July.
The porn I was watching was the basic Riley Reid, Adriana Chechik and Megan Rain my favorite porn stars. But I eventually got into a category known as “stuck porn”. This is where the sibling gets stuck doing something and then gets banged. Once I started watching stuck porn I was jacking off 3 times a day.

Now this is where the event happened. I was horny as hell. I got tinder to find a quick one night stand, but that didn’t work. I even went on the outskirts of my town to find a hooker and found nothing. But the day that changed my life forever arrived. My parents and my brother and step brother went out for a day long fishing trip. So it was just Jamey and I home alone. I woke up to yelling! I rushed downstairs to see what happened and Jamey for some reason tried to go through the dog door when had for some tik tok video she was recording.

And let me tell you. Jamey was a bad bitch. She was about 5’8”, an athletic/thick body, beautiful tan skin, silky smooth legs and an ass that hypnotizes you. I was just there starting at her ass in those small volleyball shorts until she yell “are you going to help!?” I said yes, and processed to take my pants off and slowly started to jerk off. She kept trying to get out, and then I eventually got close to her and started sniffed her ass and burying my nose in it. She asked what I was doing and I told her I would help her out. I pulled down her shorts, and started to eat her pink pussy as she started to moan, I spat on my dick to lube it up and stuck it in her, and started to thrust intensely as she made those sexy little moans, I kept pounding her pussy until I accidentally came inside her and my cum started to droop out of her pussy and some running down her leg.

I dropped to the floor, it felt like god kissed me and I was high on dopamine. Until the post nut clarity hit me and me sister started yelling at me to get her the fuck out, but I was frozen. She eventually wiggled out and ran to her room. I was in my room playing games until my parents came home, then that when I heard them call my name and got chewed out. I was kicked out of the house, my sister wanted to press charges on me and I got disowned by everyone in my family. I tried to help her but I misunderstood. Am I the asshole?

Tldr: Dad got divorced, we moved to a new town, dad started dating a woman who had two kids (a boy and girl), they got married, I banged my step-sister and got kicked out.