Hi, Today Is My First Day Of My Period And

Hi, today is my first day of my period and I started feeling back pain from Yesterday. Finally bleeding started after 11 am today. This bleeding is not normal as oppose to my other periods. the amount of blood is very insignificant. what is the cause behind this? note . my periods are normal and last month i had it on 10 th. we are trying to conceive and i have been experiencing slight backpain and tiredness for the last two weeks. please suggest.