Im sad but i dont know why?

At the end of (almost) every day, i keep end up being sad and i cant tell why. its either a mix of pent of emotions i didnt realize i had, or something else. I want to cry but i dont even know what about.

Even sometimes throughout hte day its like- im forgetting that i exist? like im here and experiencing things but it doesnt feel connected. Like instead of me being ME, its like im stuck in my head, and experiencing everything through a film, if that makes sense.

This isnt just a me thing right? There has to be a reason for it and stuff..?