Madam,
There are two things 1) whether you are covered under ESI Act or Maternity Act. Check this and confirm and 2) Obtain the certificate from the Regd.Medical Practitioner mentioning the facts and Likely date of delivery.
Is't possible for you to wait little more, as the amendment to the Maternity Act is expected any time and you should take advantage of any favourable provisions forthcoming. I won't suggest you to take a risk but , if possible only. In any case you can avail 6 weeks of ML before your expected delivery date (pre-natal) and another 6 weeks after the delivery (post-natal). You should have intimated your employer in the prescribed form about it as required. Pl.refer the Act. for adequate compliances immediately.