I was in this situation two years ago.
I wasn't happy with my AS results I got at my Sixth Form but I still got through to A2. I didn't try for A2 and as expected, didn't get into University, even though I shelled out for re-takes.
So what I did was apply to college for a Level 3 BTEC and as of now, actually put as much effort as I could into it and came out with a DD*D* (A*A*A equivalent) and am just about to start Psychology at UofManchester.
As MarvelAgent says, you're not the first and you certainly won't be the last.
I'd like to add on that if you wanted to go to University, you've still got time to do retakes and boost your grades - and even if you don't get the A2 results you want, there are still a variety of options that will lead you onto a University Course.
In regards to seeing if you can carry on with Economics, talk to your teacher/lecturer, they will know what is best.
Above all though, stay positive and start planning. So you didn't get the results you wanted, it's not too late to do anything about them