Bullying and anxiety about being vulnerable/authentic

I went through a pretty traumatic bullying experience around ten. I had a best friend who I loved and trusted more than anything who started telling me I was disgusting, a monster, evil, that I deserved to d ie, and telling this to my other friends too, then turning around and acting like it never happened or she was sorry, then it starting all over again. It continued for a year and a half until she left, and moved without an apology. My parents had me in counseling that young because I was so afraid of making new friends and meeting other people I just didn't speak.

When I did get enough confidence to do that, I would get very excited about my friends, want to talk to them all the time, fixate on certain interests of mine and talk about them a lot. I think it annoyed people or wore on them somehow. So the friends I did make would often snap at me. They would tell me to shut up, that I was obnoxious, annoying, overbearing, Some even continued to tell me to o ff myself, and it was very hurtful. Every time it was when I thought I could trust people with my personal experiences and share with them, but I really couldn't in reality without being criticized or made fun of. I still remember that the guy at our school, who got the superlative for like "nicest person" or whatever told me "this is why no one likes you, you literally never shut up about you stupid class" when I was talking about how much i liked my one course i was in. The nicest person did that, apparently. It was painful. So eventually I think I got to a point where I stopped opening up to people about things I actually enjoyed or wanted to say, because I just assumed they didn't want to hear it.

I'm now an adult and a very reserved person with my emotions, and I don't open up much. I'm afraid to tell people what's really on my mind because I don't want to get hurt or judged or attacked again, and because I don't want to come across as someone unlikeable. It scares me to open up to people even if they seem very very safe, especially if they are more outgoing and social people, because they remind me of the people who were so friendly to everyone, but then really cruel to me I guess. I'm afraid because I just have this gut feeling that they can't really be that nice, they must be lying or tricking me and will get angry with the way I am eventually.

Are there any tips people have for feeling less afraid of opening up to people, and being authentic and vulnerable, after being hurt specifically for being so outgoing and authentic for so long? I want to change and feel more free to express myself without being so afraid, I'm going into a new romantic relationship and want to be more true to myself this time around and not so scared to be judged all the time, and I also think it will make it easier for me to make friends and build connections.