I want to become an economist.?
As in a research economist, working in academia or government departments or think tanks? Then you need a graduate degree in economics or mathematics. If youre in Europe, your best bet is to enroll in a master program in economics at decent university. With a good GRE score, you may be able to get in despite not having an undergraduate degree in economics. Do well there and apply to suitable PhD programs. If youre in the US where terminal masters degrees are more rare, attempt to take college level math and econ classes, and ideally try to get experience as a research assistant. This may be difficult if youre not affiliated with a university, which is why you may have to go back to college. Another better but more challenging option is to apply for the MBA at a business school that has a strong econ department (Columbia, Chicago Booth, MIT Sloan, and NYU come to mind), and take as many economics and econometrics classes as you can, enroll in a PhD following the MBA. You could try to apply directly to PhD programs, but it will be very difficult as many applicants have strong backgrounds in econ already.