To me, based on what you've said, it sounds like you just have lower emotional awareness that you would like to have. That's ok. It doesn't necessarily mean you have dysthymia, although that is also possible. It doesn't sound like it greatly affects your daily life, so I wouldn't necessarily recommend seeing a therapist right away. But I would recommend looking up whatever you can about creating emotional awareness and empathy and things like that.

If you find things that help you understand and recognize your emotions more, great! That sounds like all you'd need. But if you find it too difficult, or find something's blocking you from going any deeper, THEN I would easily recommend a therapist. A therapist could help you explore your emotions, and any possibilities of anything in your past that may have blocked them off.

However, I would also suggest that there's no need to be alarmed by any of this. It's ok to not be happy, or to not know when you really are happy. Emotions are tricky things. There's nothing wrong with you. I hope that helps somehow.