I'm seeing a lot of myself in the OP's new boyfriend (if you could call him that). I, too, feel deeply in love with my first girlfriend after just one date with her. I felt like I met my soulmate, was willing to fully commit to her, and build a life together. Mind you, I wasn't physically attracted to her at all, and honestly, was bored with her most of the time. Her not being attractive was a good thing in my mind, because I found it easier for me to believe that she liked me. But I was still grateful to have her in my life. Like the OP's boyfriend, tried to rush things to get serious as quickly as possible. As expected, she quickly lost all interest in me, to the point of not wanting to dance close at a dance we attended.
While I had the social foresight not to say any of it to her face, I felt all of it in my mind. I was also telling everyone I knew that I had a girlfriend.