Delay in Periods, or lighter periods or even absence of periods in the first 4 months of Saheli usage is absolutely normal. In fact this is a good indication that Saheli is working for you. Basically Saheli suppresses the growth of the inner wall of your uterus, which is very much needed for successful pregnancy.
If Women doesn't get pregnant, this inner wall of uterus beaks down and sheads and this is called periods.
But in case of Saheli, the inner uterus wall is not allowed to grow, hence you get lighter periods/delayed periods or even absence of periods. Continue taking Saheli and after 4-5 months, your periods will normalise.
As long as you get a negative result in pregnancy test, nothing to worry.