What should I do if I feel like my shyness is ruining my life but I don't know how to fix it?

I feel for you. Shyness is ruining my life as well. I hate it. I wish I could be outgoing and have good self-esteem.

What is wrong about being shy? Correct - nothing.

That shyness isn 't the problem.
I know a lot of people who are shy but liked
by a lot of girls & boys.

I guess the problem is deeper in YOU.
Am I right, that you're not that confident?
You seem to be shy because you are scared
of people, conversations, and so on..
A reason could be, that you want to give like
a "perfect answer" all the time and that is why
you prefer "being quite" to "talking".
Moreover, I guess you don't like yourself and just
think of stuff like "she doesn't like me because of my looks",
"they don't like me because I am not that cool" and stuff like that.
AM I right?

Well, you got a problem.
BUT because you know now,
you already made the first step.

Be yourself, that's all that you can be!
If you wanna talk to a girl, do it!
If you wanna go out tonight, do it!
You choose!

Stop thinking of "what would be the best to answer now?" !
Start talking to the ones you wanna get to know.
You got nothing to lose!
You got only 28.000 days to live..
Enjoy it & have fun.

Workout and gain muscles trust me it boosted my confidence levels and I'm a shy guy as well so your not alone

Go out meet more people, experiment more and more...i am trying the same way.