I know exactly what the problem is.
The issue is that you are spending time 'getting to know' the girl before you make a move. If you go in making friends first, then quite obviously you are going to be put in the friend zone and not thought of as much beyond that - of course there are exceptions, but in general, and that's what it seems to be in your case anyway.
When you first meet a girl you fancy, you need to make your intentions CLEAR FROM THE START. At university, I can put the guys i've met into two categories. The ones who immediately hung out with me, became good friends, chatted to about other girls etc. Now some genuinely weren't interested in more, and we're excellent friends, but a couple of others then tried to make a move months down the line, and it's like, no - we are just friends now, I don't see you like that.
And then the ones who are confident... and how do I put this, 'alpha like'(?), who meet me, get my number, and move very quickly onto a date or kiss or whatever within the next few days - letting me know they're interested as soon as possible. This is the way to go - it's cliche but confidence is sexy, and it works the majority of the time! Of course it doesn't work all the time, sometimes they're not my type or we don't click personality wise at first, but it's so so so so much better than pretending to be a friend for ages and then hitting on a girl. If you get rejected, then it's so early into meeting the girl, you can be friends without any of the awkwardness or one person pining secretly over the other.
This is just my experience and a general thing I've noticed, but I hope it helps!
Edit: So to sum up, you need to MAKE YOUR MOVE VERY VERY VERY EARLY ON.