Hello Mam I Am 13 Weeks 6 Days Pregnant But

Hello mam I am 13 weeks 6 days pregnant but my ultrasound showed that I should be 16weeks pregnant so there is gap of 2 weeks 6 days and my lady doctor advised me to take fertigyn 5000 its choronic gondatropin injection and nidogen 500 its hydroxyprogestrone injection once in a week ..pls suggest me what to do and my period was always irregular.