Should I Get Tested For Delayed Period?

Hi doc, I am 26 married, we follow a natural process to have intercource, that is we have unprotected intercource from my 18th day of period to the next period cycle, generally my periods get delayed by 1 week every month, but this time it is more than 10days, i have performed the pregnancy test in the early mornign but it was negative, can u please suggest why is my period delayed, is it required for me to get the tested with a doctor?