If your salary is below Rs 21,000, you will be covered by ESI Schemes. Whether you have hospital facilities extended to you through your husband is immaterial. The company cannot exempt you from ESI coverage. Whether you take the benefits from ESI or not, you should contribute the required 0.75% of your salary to ESI.
An important note:
Will the Central Government Health Scheme give you (as a beneficiary attached to your husband) compensation for 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 (though I am not sure if it is available), but I doubt whether the dependent gets any monetary benefit. Under the ESI scheme, you will get medical benefits right from day one of your joining. You will receive 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 benefits 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.