If your salary is below Rs 21000, you will be covered by ESI Schemes. Whether you have hospital facilities extended to you through your husband is immaterial. The company cannot let you out of ESI cover. Whether you take the benefits from ESI or not, you should contribute the required contribution of 0.75% of the salary to ESI.
An important note: Will the Central Government health Scheme give you (as a beneficiary attached to your husband) compensate the loss of income (salary) for the days you remained on leave due to sickness? True, you will get medical benefits, and even super specialty treatment (I am not sure if it is available) but I doubt whether the dependent get any monetary benefit. Under ESI scheme, you will get medical benefits right from day one of your joining. You will get full salary and medical assistance including super specialty treatment in case you meet with any accident during the course of employment. You will get monetary benefit based on your salary for the days you remain absent due to sickness, once you complete 9 months in service. These are some of the basic benefits available to an ESI covered employee. There are other benefits like unemployment benefits, extended sickness benefits, benefits to dependents etc.