I got my first natural period but why the 2nd month period is delayed?

Since you have got your first natural period, it indicates that your ovaries have become active & the medicines are working. But it is not necessary that your second period will also arrive on time. You need to have two things here, Trust & Patience. 

Periods will slowly regulate during the treatment. To support timely recovery & get freedom from your period problem, take the medicines without any gap, follow the Gynovedic diet & do a little exercise daily.