This is a little more accurate than most. It's not that I'm depressed... I mean sometimes I am if I dwell on shit too long... I mostly just don't feel anything.
It’s unreasonable to expect a lifetime full of happiness, that’s like wanting to be afraid 24/7 or laughing 24/7. Instead, work on being purposeful and contribute to your social setting (friends, family, community) being known as a reliable person will give you contentment while you go through life. Being content will allow you to perform your responsibilities while you experience a whole myriad of emotions; you’ll be bored 10% of the time, happy 10%, sad 10%, anxious 10% etc. And that’s normal.
Uncontrollable happiness all the time is called being manic and it should be medicated.
Depression is hard to pin down but there are a number of symptoms you can look into, dullness is one of them, even if you can laugh and such. But until it starts affecting your life like maybe you start forgetting more things or have thoughts of self-harm or suicide, there's no reason to freak out about it.
Uncontrollable happiness all the time is called being manic and it should be medicated.