I can't feel love nor sadness. Only joy (?)

It’s not stupid. I think you’re just overthinking it, enjoy the joy you have try not to dig yourself into a hole with a question like that. Joy is good! One thing to note though, Joy is just an emotion, like sadness, and will come and go throughout your life. Where there is joy, there will necessarily be sadness to contrast it, that’s what makes happiness all the more special. The end goal is to be content and comfortable with your choices because they suit you. Best of luck to you moving forward!