Yeast infection common in pregnancy?

i am 16 weeks pregnant and i am getting white discharge not all the time as sometimes its just clear ... but in my nickers it is white most of the time.. is it a yest infection and shud i go to the doctors? orr is it normal ? and are yeast infections common in pregnancy? had to ask on here first as it is really hard to get into my doctors takes upto 3 weeks to get an appointment.