How do you know when you’ve found “the one”

I have been single for the last few years and honestly enjoy being single a lot, but recently as my friends get older and start settling down I’m beginning to feel like the odd one out. I have met a lot of great people and had fun short flings but most of them have ended up wanting a serious relationship after only a few dates and I have not been able to commit due to enjoying being single and not feeling that major “spark”.

Right now I am seeing someone really great and we’ve hung out about 4 times. She is honestly a total catch and seems really great and is definitely the first person in a long time I’ve even considered being in a serious relationship with, but I can’t shake this feeling that I’m not completely head over heels for her. I’m at a stage in my life where if I commit to someone I want it to be for the rest of my life, and I just can’t honestly tell if I would be happy with her forever or not. I know it’s early in the dating stage to be thinking about stuff like this and I know I need to get to know her better before making a rash decision, but this is more just background context for my general question. People who have had long term relationships either last or fail, what did it feel like early on when you were first dating? Was it an immediate “this is the person I want to be with forever” or were you unsure and just decided to go for it and commit anyway? How did it work out?

Thank you in advance 🙂