Measuring Cervix & Suppositories

Starting at 16wks they are going to start measuring my cervix length to monitor and watch for any changes or shortening. Due to a previous preterm delivery. How do they do this, through a US scan? I didn’t think to ask at the moment my appointment was chaotic with my two children in tow. Also I have severe morning sickness and was given suppositories, has anyone taken them before to deal with morning sickness?! I’ve never done a suppository for anything. So I’m quite nervous.