I completely empathize with everything you said.
I started feeling this about three years ago. I was 20 at the time, and I had mixed feelings regarding my future career path. I also began to wonder why I was procrastinating everything, a habit that had been with me since early adolescence.
As I continued to ask questions and delve into the deeper aspects of my inner self, feelings of ennui, emptiness, and dissociation grew within me. I used to have all sorts of dreams and aspirations, but everything gradually began to fall away.
I thought that the problem could be external, that I needed some goal to aim for, or some activity to dedicate myself to. I tried a multitude of life paths, trying to find something that would click. Nothing worked; I would get initially excited, and then it would peter out relatively quickly. Moreover, the period of excitement got shorter over time, eventually only lasting a day or two.
At the same time, I believed that the problem was also internal. Over the past three years, I've spent literally thousands of hours sitting (or pacing) in my room and talking with myself about myself. I questioned everything I believed; I looked at every possible nook and crevice of my mind that I could think of. I foolishly thought that if I just kept pushing, I would eventually ascend to (or even accidentally stumble on) just the right insight, some optimal sequence of words or statements that would put me in a frame of mind that would lead to an escape from the emptiness that had grown within me.
Well, after three years, the realization I've come to is what you said in your post (the three years gave me the certainty to come to this conclusion). There is no meaning, and it's a fool's errand to search for one. That doesn't mean, however, that happiness is not possible or that we shouldn't live in spite of it. I recommend reading up on "absurdism." It corresponds quite closely to what I've arrived at myself, and might corroborate your experience as well.