i find myself in the same boat many times. Feeling like there is no point to living really. Feeling like there is no point but to please others. Feeling like the world expects too much from me. Feeling like I don't owe anyone a single thing.
Well, It's not until I read from the Bible and pray that the perspective changes. Many times in the Bible, there are examples that speak of serving. I don't know if you understand that, the Christian faith or Jesus' ministry was to serve.
He didn't come to this earth to serve himself, to establish a kingdom for himself even though it was rightfully his to take. So, in essence, what i'm trying to tell you is that, The whole point of living on this earth is not for yourself, it's to serve others.
That's why it feels like you owe everyone something, it's because everyone who hasn't put things into persepective feel like you owe them something.
There's also that feeling of happiness when you know you've benefited someone else, I know you said you didn't want to be happy, but try it out. Even if that person doesn't appreciate or show appreciation for what you did, know that you good for that person, Don't ask anything in return or expect anything in return either. It's addicting

I don't know if that helps out at all, and i understand you're an athiest, and don't believe in God, but i urge you to talk to me or someone who can show you the plan of salvation.