It sounds like what you keep doing is holding back until it all comes pouring out. So by the time you let your feelings be known, your girl is already no longer thinking of you as a potential partner, and then you dump all the stuff you've been holding back in her lap and she doesn't know what to do with it.

Warning, guy talk ahead.

Screw fate, destiny, 'meant to be', and all that other crapolla people tell themselves about why things sometimes work and sometimes don't. The thing is, it works or it doesn't just like a building stands or falls, or just like a car runs or stalls. You have to build it right from the start or you can expect failure down the road. You have to maintain it or it stops working like it used to. You have to keep putting work into it (changing the oil, air filter, and transmission fluid so to speak). You have to replace parts as they fail, and you have to continue to build it up (like you would install a ceiling fan or remodel the kitchen) and keep it fresh and new.
But first, you have to have a foundation. Then you frame it out, and then put up your facade and roof, run your electricity and plumbing. And all of this has to be done before you can finish the walls, floors, and ceilings. finally you can get down to installing plumbing fixtures, receptacle and switch covers, lighting, wall texture, paint, wallpaper, and all the other finishing touches. It's a process, and you have to do it in order.
Or another way to look at it when you're just getting to know someone: it's a lot like mental foreplay. You can't just jump right into the final act.
Start letting her know you may be interested early on. Flirt as you're getting to know her. If she responds in kind, and things continue, great. If not, no big loss; there are other women out there, and just because you're not Mr. Right Now doesn't mean you might not be Mr. Right.

None of that is to detract from what others have said; it's all sound advice. I'm just offering a different perspective.