I have always had regular periods. But this time I missed them. When I did my pregnancy test after 3 days, it showed a negative. I want to conceive. I am quite tensed . What does it mean please help

It means that you took your test too early. Rule of thumb is to take it when your period is two weeks late using first morning urine.

Does taking NINEFOL TABLET before pregnancy of any harm to the menstrual cycle?

I'm not aware of that medication. What are you taking it for?