It sounded like you're going through an existential crisis, of sorts. Now, I'm no Dan Howell, but I've had my fair share of existential crises. And at least I can relate to you on the fact that it does really suck.
The love thing, I'm clueless. But I hope it works out, one way or another. I don't know how to be useful to you on this matter with my amateur advice and limited experience, but I will tell you to try not to force your feelings. You will feel what you will feel, whether you like it or not, so there is absolutely no point beating yourself up about it.
If you don't want to do anything about it, just enjoy her company and being around her till you eventually get over her and laugh at your past self. Nobody is perfect until you fall in love with them. It may be painful, but enjoy this time and make full use of the happiness she brings you.
I did say my advice may suck.
She is pretty great though.
As for the existential crisis thing, I know far too well where you're coming from. I don't know why I'm doing what I'm doing. I don't know if I want to be a lawyer. I don't know what I should do with my life. And I don't expect myself to know what I should do with my life at 16.
The other day I realised that I have no dreams. And by that I mean you know how some people have crazy dreams? About becoming a famous singer or astronaut or something? Something crazy, that probably won't ever happen but yet you spend every waking hour thinking about it? Yeah. I realised I had none. I had no dreams. I had read about them, heard about them, watched Disney movies that glorified them, but I didn't have them. I mean like I do have dreams like meeting Dan and Phil, and living with you, but I didn't have something that I wanted to be if the world was ideal. This means that I had just resigned to the path laid down for me and not even thought of anything crazy that I wanted to do with my life.
But now, I think I do. I don't think I'm going to mention it here for now, but I think I have a dream. It may never come true, but it's still there. It feels new, but it feels amazing. I still don't know what I should do with my life, but I think I finally know what I want to.