I used to have selective mutism when I was a child. I don't know if you also have this, but you seem to be going through some of the things I felt. I was always very close to my sibling, and she was my play buddy all throughout childhood. Naturally, I did not feel comfortable when I was plopped in school with strange kids, so I just sat through classes counting minutes until I could go home and be comfortable in my familiar environment.
Once in a while when I was put into a position to speak up, I was not sure what to say so my voice would be many decibels lower than how I normally speak at home. This made my peers and my teachers request me to repeat myself and I would blush and then speak in even more muted voice. Soon I just decided to not bother talking at all. I was so self conscious of my voice that when boys would annoy me (as they typically do to girl) by poking or throwing little things, I would not protest as it would require making noise. This encouraged a few boys to be mean to me because they knew they can get away with it without getting into trouble.
To this day, I don't know what triggered my selective mutism. I had a pretty happy childhood, and no traumas or anything like that. I have a naturally introverted personality, but many introverts are fairly well adjusted in schools. Whatever it was, it just spiraled out of control and slowly I was talking less and less. I remember a few teachers making attempts to pull me out of the hole. A really kind teacher in my 3rd grade would try to make eye contact with me, and then when our eyes met, she would give me the biggest smile. I think that kind of attention made me even more self conscious and made me withdraw even more at first, but I think she was the only teacher who was able to help me out a little bit because I felt more comfortable with her.
I also never laughed in public. I would try really hard to hide my smile if something funny happened, and sometimes I would burst into giggles but I would cover my mouth with my hands.
But enough about me... what i want to tell you is... you will eventually grow out of it. I did. For me, it was a slow process but the toughest part was finding that motivation to speak. I found that I had no problem doing well academically or even making a few friends (introverts do clique with each other) and I had no interest in doing overtly social things like becoming a cheerleader (LOL) so I did not really see my "handicap" as a problem. But the big kick in the butt happened to me when I was applying for colleges. I was doing well academically, so many good colleges were interested and wanted to interview me. I had zero interpersonal skills, especially with a stranger, and I failed these interviews. How do I know that I failed the interviews? Well, the colleges that interview sent me rejection letters, and the colleges that don't accepted me. I think that was the moment when I realized that my fear of putting myself out there in public and therefore taking the lazy roundabout ways to cope was not enough, not to mention incredibly stupid. I realized that my fear was preventing me from reaching my full potential, and that made me extremely angry about myself, and then it motivated me to do something about it.
I wonder if you are also falling into the pattern of feeling lazy to tackle your issue and finding roundabout ways to cope. You did mention that you "socialize" online. That's a cowardly way of dealing with you fear of speaking, isn't it?
My way of pulling myself out of my situation was by self-torture (LOL). I kept signing up for things where I would have to talk.. for instance teaching duties or public speaking duties. I took classes that required giving presentations and signed up for jobs that would make me interact with 10-15 students where I would be forced to talk in front of them, and then to break them down into small groups and talk to them. I would initiate gatherings or group outings and force myself in social situations. The first time was the worst - I was so nervous and visibly shaking at the students actually felt bad for me. I was holding my water bottle upside down as I spoke and the entire contents spilled on the floor and I did not even notice. But each day you force yourself and tackle everything head on, it gets better. Things just get better and familiar with practice. You will never be as comfortable as when you are sitting down with family at home, but you also learn to adjust and set realistic expectations and goals.
I still don't see myself as an extremely extroverted person, but nowadays when I introduce myself to a new acquaintance and mention that I'm "shy" they laugh in disbelief. So I think I made a pretty good progress. I am still an introvert which means that I do not speak my inner deep thoughts until I am comfortable. But I picked up a few skills where I can be surrounded by a bunch of people and still talk to them. I find that if you practice a few interesting stories and recite them, that helps break the ice. People like being asked about what they like to do... so you can keep talking about that too without drawing too much attention to yourself. And finally, the bit about you worrying about you being judged by the sound of your voice and your laughter - that fear will never go away, but at some point you just have to create an attitude that says "if they judge, to hell with them!"