Hi, We Are Trying For Baby. My Last Period Was

Hi, We are trying for baby. My last period was on December 4th. My period cycle is 28/29 days with regular manner. my next due suppose to be January 2nd. But i missed my periods.when is the right time to check UPT? Addition to that i feel cervical itching(crazy) I feel very uncomfortable with that. What is the causes and what should i do? Really embarrassing