Why is it hard to talk about myself?

Lately, I have been having difficulties with my thoughts, but as much as I want to talk to someone about it, I just can't. It may be a mix of not wanting to burden anyone and also feeling as if my thoughts are silly. Even if I knew a definite reason, it doesn't make it any easier to open up. Which led me to wonder why, why is it hard for me, and possibly others, to open up. So I have decided to explore this while also exploring one of my lingering thoughts of late. I was going to research this and see if I could find studies or books that could answer this. However, I wasn't sure if that would be interesting. So this post turned into a personal musing. One of my lingering thoughts may link into why I find it hard to talk about myself. The thought is "are they really my friend or not?", I used to have this thought often but this is the first time in a few years it has cropped up again. Being autistic it is difficult to tell when someone is my friend or not. I believe I made some new friends at uni, everything was going well and I didn't have any doubts until a week or so ago when my conversations with those friends stopped somewhat. They haven't spoken to me much at uni, or over messages, which caused the thought to come to the surface again. For a few days I tried to work out what I could have done wrong but I couldn't think of anything. The thought has dwindled now, however, I am still wondering if something has changed and they aren't my friends anymore but I think they would tell me if something had happened between us. A TikTok I watched helped a little with that thought. It said something along the lines of; No one is mad at you. If they are, they will tell you, and if they are and they won't tell you that's not your fault. If they care and want to fix it they will talk to you. Perhaps not knowing if someone genuinely likes me affects my efforts to open up. I do try not to talk about myself to those I don't know very well due to the fact I don't want to over-share. Conversations rarely come easy to me too. Another reason I can think of that may lead to a reluctance to open up is; trauma. Past abusive relationships led me to feel that I don't deserve to be heard, that my problems don't matter, that somehow everything is my fault. So, I just don't talk about things. In March I am starting counseling at my university, it will only be around 8 sessions though. I'm hoping they can help me a little and then point me in the right direction. I hope to get therapy properly but I will have to go private, so it's just being able to afford it. Do you find it difficult to open up? If so, how have you overcome it?