I think what you describe sounds like classic depression and anxiety, and it wouldn't hurt to have it evaluated by a professional. People with normal, full lives are plenty susceptible to depression and anxiety. It doesn't require trauma or grief to develop. In fact, most of the people I've known in my life who have serious depression lead extremely normal, otherwise comfortable lives.

It sounds like you've managed to deal with these feelings for a long time, but maybe are starting to be more concerned? More interested in making some changes? If you can afford it, I would be all for talking to a mental health expert. It's very possible you could benefit from it, and reduce a bit of this "something's not quite right" feeling.

Thanks for sharing this. I know it's sometimes hard to just pour it all out, even among strangers. I hope you can find some answers soon.