How do I fix this?

I’ve been really dealing with self esteem issues, my social skills are bad. I tend to be quiet, and reserved but recently I’ve been trying to be more outgoing. I’ve isolated from my friends and family members. My brothers and sisters are distant, they have their own lives and moved away. My oldest sister is very mentally off so I don’t talk to her, she talked shit about every one of us spreading lies so I don’t associate myself with her. Anyways, I have a teenage nephew who lives at home here and I used to be close to him but now it’s hard to even talk to him. I worked in the hospital around nurses my age I’m not a nurse I’m a patient care tech. And I kept myself busy, and I rarely ever said no. And I think I burned myself out. I was ‘agreeable’ from what one said lol. I didn’t care tbh, I just wanted to stay busy. But I felt like I was treated like a kid, maybe it’s my own demons thinking that. But I felt like they thought they could get me to do things other techs wouldn’t do. That’s what I want to change, they all hung outside of work so they would get sassy with one another. I never said no, and sometimes they got bossy. And I said “I’d tell them” when they got bossy or whatever. One said “just say no, you are too nice”.
I am not nice, I just avoid confrontation. I am now at a new job, and I’m quiet again because I’m new. But I don’t want this to happen again, I’m 27 and I feel so lost. I don’t want people thinking I’m like “slow” or what not. Now I’m giving medications, if I was slow or impaired would I be able to do this? I’m so worried everyone thinks I’m “off”. I’ve been to a few therapy sessions and they say it’s anxiety but I’m just confused. Am I digging deep into this? What are some ways to be confident? In the workplace and out of the workplace?
Updates
3 d
Can I solve this by myself?
How do I fix this?
Post Opinion