How do you know if feelings toward someone are real, or you are just vulnerable, in the dating phrase?

I am 28/M. I had a breakup one year ago, from a 8 years old relationship. When I felt better, I started to date around november, but did not like any of the girls, did not feel comfortable. I met a girl in December, and we were really vibing, we had three dates but she told me she is not ready to date yet. I felt really heartbroken, and I felt that I love her. Obviously, it is too much for 3 dates. But we really were vibing, and I really liked her company, and wanted something from her.

I knew my feelings are not normal, but I felt I was over my ex. This girl contacted me in March, to meet, since I told her in December if she want we can meet later. We met once, and told me it won’t work. And I felt really bad again, because I thought we were vibing and thought she likes me.

THe point is, I still think about her until this day. I cannot forget her for some reason. I am dating now with others, and I Am much more cautious than before.

But I Am not sure if I really feel something toward her, or just met her at the wrong time. She was better than the other dates, and I thought she likes me, also I was vulnerable, so maybe this was the recipe for a perfect heartbreak. But why I still think about her? Is it really this dangerous to date someone you like, when you are vulnerable? Why I cannot forget her? I think about her more, than the girl I had a 8 years old relationship with.