Metaphysical Meditation

I wanted to ask you a question about metaphysical meditation. I think that is what it is but am not sure.
Since I was a child I have on occasion meditated on the physical universe and all existence within it. Visualizing it’s vastness in my mind. I then try to bring my focus to the outside of that universe, to the outside of that physical space. What was there before the universe? And what space is that space since it cannot be the physical universe. If it was not here there still must be something or is it just nothingness? Unbeing…is that possible?

Thinking about that visualization and focusing on that meditation brings on a very overwhelming feeling which is indescribable. I think it is fear or anxiousness. I am not sure. I even physically feel it right in my solar plexus and the tingling sensation has been so strong that I have to stop the meditation at times.

However on 2 occasions the mediation ended in an overwhelming feeling of happiness or satisfaction I am not sure again. The first time this happened was when I was about 8 or 9 years old and it was the first time I thought about it. I wondered what would there be if none of us were here including the universe. What would be left and the meditation left me with an actual high. Since then it has happened one other time.

Could you please shed some light on what is going on? What is it that I am trying to conceptualize and why does it give me such a strange feeling? I am a Buddhist in philosophy but am not familiar with all of the various dogma from the lines of teaching. I simply try and follow the simple tenets and mostly the teachings of the Dalai Lama and a few other Buddhist teachers such as Geshe Kelsang Gyatso.