Unclear Speech

I am 16-year old. The problem is with my throat that whenever I speak, there are so many cracks and nervousness of fear of saying anything wrong or fear of people noticing my disorder. Some also said that I speak through my nose (not offensively, but informing). That whenever you speak there is more voice coming out of your noise than your mouth (I hope you know what I mean). This is not my born disease. Well, according to google:

1)- lefties get more speech problems than rights and I am lefty.
2)- Some go through speech problems during puberty stage.

A lot of people have trouble understanding me, and thus I don't get to make a lot of friends. I'm really embarrassed to sit with my family because they are not very helping either. They try to hold it back but eventually they become so sick of me that we begin shouting to each other. Some say I'm not loud enough, which is somewhat true. My speech is the only matter right now due to which I am 90% antisocial. They say you gotta fix the problems with whatever's holding your voice hostage. I really hope that you have the kind of help that applies to me. My voice has become so disastrous that whoever meets me, never wants to meet me again. Thank you for your time in reading and consideration to my issue.