Why am i mean?

Going into 2023, I really want to get better. I feel like i’m so mean sometimes to my family members! like I reflect at night and just think about being sassy and selfish all the time. I feel like I might be on the spectrum? or bipolar? like I can’t control it and then afterwards i’m like wtf. im only like this to my family. everyone else im super shy and quiet. please someone help me. I want to be nicer to the people I love but I feel weird expressing love sometimes. idk what’s wrong with me