I am presently drawing a salary of 15k including allowances life traveling expenses etc..I am 31ys,is it low?

Compared to my age is it a low salary? I am doing a outdoor pharma sales job.My qual. is also poor like I have only a B.Sc (Pure) Pass Graduation from Calcutta University.My age is 31.So I cant change company easily at this age.Since in pharma field to work as a Med Rep u have to be within 26 max 28!!!
How can I get a better paying in-office/managerial job?
15k pm and not per year!!!