I was wondering what you meant by 5+ calculus courses. I see that UCSD requires a three course sequence Math 10 A,B, and C or the more challenging Math 20 A, B, and C. Have you had precalculus? Then presumably the intermediate micro and maybe macro require the calc as a prerequisite. Are you likely to do well in Math10A?
You should know that UCSD econ is especially math intensive at the grad level, and it looks like their undergrad offerings have some expectation of more math than you were expecting.
Will you be enrolled in Math 10a? Then you might consider trying out this major to see how it goes. If they accepted you into the major, they must think you are prepared.
Note that econ majors at some other colleges do not involve as much math.