What Causes Lack Of Bleeding During First Two Days Of Menstruation?

dear sir i am rajani my age is 27 and i am not married i had problem like this i will get my periods monthly but if suppose i got my periods in 18th means next 2 days no flow will be there only littel bit spoting only wil be there and 3rd day onwards normal flow will start and will contiue 2-3 days. and i consulated 2 doctors they said due to hormonal changes like that. and i am scaring for my future also due to this kindly help me