How do you handle huge regrets?

I’m 20 years old but already have alot of horrible regrets that
eat me up everyday. Basically it’s all because I have social anxiety/shyness problems and that’s caused me to miss out on so much that most people my age experience. I remember being a good student when I was younger but couldn’t go to high school because I was too afraid and ended up missing out on everything; all those special life experiences, friends, relationships, growing as a person…even my education. I just feel like I wasted everything:( Everything I could’ve had and done and been. Everyone my age has memories and experiences and everything about growing up and I have nothing but these petty, childish fears. I feel like I can’t do anything, not even the most basic thing like talking to people. Let alone have a relationship with anyone…I messed up everything in my life, all the chances I had, and now I don’t even have any friends because of it. The people I used to know back in elementary school (which was my last school experience) have all gone off to universities and have had all those teen experiences and going off to bigger things and I’m still just..nothing. I recentely tried to at least take some classes at a community college but I even ended up getting the door shut in my face with that too. and the only classes I could get into, I chickened out. Like always. So now it’s back to absolutely nothing at all:( I don’t know if anyone here can relate…but it’s just really depressing. I know I can’t take back time. How do you think I should deal with all of this? Is it even fixable. My mom says to just get over it but I can’t. It took away everything.
Please help