You might not have experienced enough negative consequences yet. Let me tell you - I've been exactly where you are Corleone. I could have written exactly what you said. I can tell you it does not get any better - it will only get worse, much worse to the point where you will destroy your physical/mental/emotional health, relationships, job/finances and may end up in jail or even dead.
Take advantage of the experience of me, and many others here, and please reach out for help like your life depends on it, because it does. You will be doing yourself a big favor and saving yourself a lot of future misery. Just like you, I used to believe that using was the only way to kill my emotional pain and give me happiness. After being clean and sober for a while, I realize it was only a temporary pleasure that caused me intense pain and suffering in the long run.
It seems like you may realize this too by the fact that you are on this site and seem to be trying to quit. This can't be something you half-ass though, and it's way too hard to do on your own. You need support/help, so please get some, run with it, and take it one step at a time.
Do this for yourself and those that care about you. You are only 21, you have your entire life ahead of you - don't throw it away. You can really have a nice, happy (truly happy) and fulfilling life. Please keep us all posted on your progress.