I doubt you're a sociopath! :) Sociopathy is extremely rare. Empathy is simply the ability to put yourself in another person's shoes, to understand how and why they feel something. It's different from compassion, although it often leads to it. It seems you have empathy, but not a whole lot of compassion. Again, I can't know your heart, but I say this because you don't seem to care much how your actions affect others even though you know how shitty and hurtful it is to do this.

It's like when people say, "It's not my problem." There is no other phrase that annoys me more than that one. If everyone stopped saying (and believing) that terrible sentence maybe this world would be a far better place. If you're hurting someone, intentionally or not, it is your problem. So saying, "I don't have any interest anymore" or "I don't care about them anymore" is just a bad excuse to me. There is no reason to cut someone from your life, and to make it as hurtful as possible - at least there is no good reason, and "I have no interest" isn't a good reason. It's so incredibly selfish and cruel. I'm not saying go out of your way to maintain the friendship. I'm saying don't be a dick. You don't need to completely sever contact and you don't need to make it as painful as possible.

I didn't know you were so young though! I remember how I was when I was in my low twenties/teens... Well, I never cut people out of my life or deliberately tried to hurt them, but gosh I was stubborn, and I thought I had all the answers, and there was never any other option everrrrrrrrr! Hahaha, sorry, I am not making fun of you, I am making fun of myself! :D You're young, man. You can work on this. Truly, I wish you well.