Am I being too sensitive?

First isaac (brother) this morning was being a dick bcuz he necked me and kept doing it and I got INSTANTLY mad. Then he smacks my ass and I'm like "dont ever hit my ass" he said "it was your back" like dumbass ik what is my ass and what is my back. Then I call my bf and he starts playing with his mini skateboard toy shit and I'm like "isaac (brother) can you be quiet" I do this about 5 times and he still doesn't and he says that he doesnt have to listen to me. Eventually I just tell him to shut tf up and he says "you cant tell me what to do" like it's called common courtesy so stfu. But i didnt say that. Then i go out to the living room and i walk back into the bedroom and my stepmom says "so you're going to ignore the pile of laundry?" All smart ass like. I say "no but I just walked out of the room and I was like nah so I'm going back to the room" I am just so mad especially with my brother. Now isaac is on my step moms good side for some reason and when I try to tell her about why I "ignored the laundry" because i had a mini attitude and I didnt want to have it with her she just says "I dont care"

Update: now he wants to get on my good side🙄🤬 a song started playing and he nudged me and started singing and smiling.

My stepmom tells me to take my antidepressants but they dont work they just make me mad as hell. I take a Mexican version of zoloft