This extrovert/introvert label is used in ways it shouldn't. Two kinds of people hide behind being an introvert: assholes and people afraid of other people, often a mixture of both. Both groups alienate people with their behaviors and thus are lonely, sometimes angry about it, which worsens both traits. They don't want to be, making contact with people exhausting. Instead of addressing the real problem, they get isolated even more or, like you, externalize getting happiness, which I bet Heroin is very good at consistently delivering.
Again: these traits are not fixed. If you think of yourself as unlikable, you will be. If you think people are all stupid (way to generalize), you will alienate other people. If you think other people are dangerous, which you might have had to learn early in your life, you will behave in a way that other people don't find pleasurable and won't choose to be around you. It's painful to think about, so people just say they're introverted.
You can accept that & change, or you can stay where you are. I myself decided to stay in this social coma for 20 years, really angry about it too, being even harder on myself & others. Didn't help. Now people (voluntarily!) call me.