One of the worst kinds of slavery is slavery to self. That's because it is completely and fundamentally contrary to your created purpose: to love God and love others. It sounds like this fact is starting to become very real to you.
I was kind of in a similar place a few years back, except I was much more complacent with my self-centeredness. I wasn't even seeking to change as you are. Instead, I had the truth thrust upon me when I read a book that turned out to be more challenging and impactful than I had bargained for.
At the core, what you're feeling is purposelessness. But it's not that you don't have a purpose, it's only that you don't know what it is yet. Plus, you are tempted—as we all are—to believe that you must give up happiness to follow God. In reality, a great deal of joy is found in living and working according to the mission that God has for you.
I am genuinely much happier now, pursuing what God wants me to pursue, than I ever was when I just focused on having as much fun as possible. And it's not that I wasn't having a lot of fun before. But the joy of how I live now is so much richer and more fulfilling. And there's so much more peace in knowing that my life up to this point was not completely wasted. That, if I died tomorrow, I have made an impact and done something worthwhile with the life and breath that God has entrusted to me. That's more than I could say just two years ago.
I recommend spending a lot of time in prayer. Make time to spend with God. You can't build a relationship without time investment. Also, From time to time, take an hour or two alone and pray individually for everyone you can think of. Start thinking more outside yourself. Pray for guidance and direction daily.
Another thing that helped me back when I was first starting down this path, was something I read in that book I mentioned earlier (The Tin Soldiers by Andrew Schwab, if you're curious). This will sound kinda hokey, but it really helped me get on track. Take a sheet of paper and make four columns.
In the first column, make a list of all your good characteristics and skills. Even if they seem small, irrelevant, or stupid. A few examples from my sheet from two years ago are diligence, loyalty, yelling, patience with people, digital art, first aid, and "hydration master".
In the second column, list your loves and interests. Again, don't filter them. Some of my examples: God, guns/explosions/fire, my church's youth group, baneposting, theology/philosophy, and self-improvement.
In the third, list things you think are stupid. A few of mine: Defeatism, worrying, addiction, PT Cruisers, dishonesty, and porn.
Finally, list any goals or dreams you have right now. Anything you'd like to accomplish or do in life, whether it's realistic or not. No filters. Some of mine were "end the masculinity crisis", "counter the porn epidemic in the church", "build a really weird car", "have and raise awesome kids", and "be the best/worst grandpa ever".
Once you've done all this you'll be able to find connections between some of your traits, talents, passions, interests, and desires. It'll start becoming clearer what God has designed you for. It might seem like an impossibly large calling, or it may seem insignificant and small (at first, anyway). It might be something that has been nagging at the back of your mind for a long time now, but that you doubted or chose to ignore.
Whether you realize your purpose right away or not, keep praying, learning, and growing. Work on removing vices that could entangle you or weigh you down. Develop your talents and skills so they'll be ready when it comes time to use them. Spend time on your relationship with God and with other believers. Help people as you're able to.
I'll pray for you, brother. And I hope you find what you're looking for soon.