I am so glad I came across your post. This is -exactly-how I feel and I would love advice as well.

Growing up I have always been a little insecure. Despite how much I’ve tried, I am still a little quiet and shy. Growing up, I was involved in many extracurricular activities including softball, volleyball, pageants, cheerleading, 4-H, etc. I was always average in these things. Despite all that I am involved in and how outgoing I try to be, I have always had trouble making friends only having 1 maybe 2 friends max. I have a very friendly and positive personality. I started a new job in February and all of my coworkers are wonderful. Everyone laughs and jokes and has a great time throughout the day. I try to be involved with them but it always seems I can’t find the words to say to join in on the conversations and jokes. I feel that this probably goes back to my insecurity. Today a comment was made that really hurt my feelings because I have been praying and struggling with this for a while. I believe that my coworkers in no way would intentionally hurt my feelings. Everyone was sitting around talking and laughing like usual. I was sitting at my desk just laughing along with them like usual but not adding to the conversation (again, because I can never find anything to say). The conversation continued as follows:

Coworker 1: “I wish I could be more like Jbo, just quiet and in my own business”.
All coworkers at once: “Noooo, don’t do that”
Coworker 3: “don’t be boring”

Although I know they did not mean to hurt me in any way, my heart felt like it crushed. I have been working so hard on talking and joking to try to fit in more. I finished my paperwork and left so that I wouldn’t lead on that I was hurt.

That's super insensitive for your coworkers to say that. Whether it was a joke or not. I'm sorry about that. You didn't deserve that. I constantly have to struggle with being the quiet one and not talking. It's horrible and gives me severe anxiety. I'm even going to ask for less hours so that I wouldn't have to deal with talking to anyone. I really wish somebody could give us the advice we need to help this and stop this anxiety. I feel your pain. I wonder how people could talk. Ugh it's super triggering for my anxiety. It's absolutely awful. I'm still waiting for a notification on how to deal with this from anyone and unfortunately I keep coming back to none. :(

I hate that label. It’s been used on me forever and I got to the point where I don’t care anymore. You could laugh at the comment as though the very idea is ridiculous or shrug your shoulders and smile and say something like “not really” or “only sometimes.” If you really do want to give someone a chance maybe ask if they’d like to grab a coffee or lunch with you. It can just be coworkers or possible friends getting to know each other.

I can relate very well with how you feel, except my situation is more social settings, especially church. There are so many people there, and at some gatherings things get especially noisy--so noisy I think it's detrimental to good fellowship, which is what the gathering is about.

I look around and see people I know working their way around a room, talking to people I don't know and everybody is talking like they've known each other for years. Then I sadly (and enviously) wonder how they got to know each other so well and wish I had more friends like that-but don't know how to get started.

Maybe like you, I might come across as super quiet and prefer to be alone, but little do they know that inside I'm hurting because I'm not that good at striking up interesting conversations or keeping them going. That in itself I think sends the mistaken message that I'm not interested.

You sound like you have done some things that typical shy people don't usually do, so I think you're more ahead than you give yourself credit for.
Could it be that the quietness others see in you is actually learned behavior from your parents? Were/are they the rowdy, outgoing type or quiet people who like(d) to keep to themselves? And if they were/are you may feel like you're too wild for your family and shocking your parents.

Does any of this make sense to you? Does it give you some insight? Unfortunately, I don't think any of it solves the problem. Remember, I'm in it with you.