Kissing a girl and feeling down, explanation?

Yesterday I drove her to my flat
We were supposed to watch a serial on neflix but we couldnt find anything interesting (I sat closely to her, touching her legs using my legs and she didnt back off)
I closed laptop and suggested we could talk
It was awkward at first but afyer a while I suggested we could hug each other
She said yes, and with more minutes we were hugging closer
She putted her glasses off and me too
We were kissing after a while and I were toucjing her legs, arms belly and back,
Her face hairs and all
We were kissing and hugging for 20 minutes
We were like laying down and doing all that stuff
I felt her breath was quick, and she was red on face
She was like, shy and oh I dont know (chuckling) but enjoying kissing and my touching
I felt very good but it wasnt something Fantastic as they show in movies and all
I dont know why
I also felt down for some time, I dont know, it was like, okay so I can do that stuff with girls, I could do it with much prettier girl than she. Like, i can find much prettier than she
But before kissing her and all, I was finding her atrractive and sexy. I sometimes were watching her on classes (like on PE class when she were wearing tight pants )
She is 6/10, with exercises, care and ect she could be a very good 7 ++/10
But my mood improved when we were driving back to her home and talking