On transvaginal ultrasound cl first was 49mm and in few seconds got down to 29mm/w funneling.i have dynamic cervix right?what its characteristics?

Depends: Dynamic cervix during pregnancy helps assess for magnitude of risk for a preterm birth. This needs to be considered in context of other factors including prior history preterm births, fetal fibronectin, rate of cervical shortening & other factors. If you're at risk for preterm delivery, cervical length <25 mm is significant & <15 mm might be imminent. Hope that helps.

What you described!: If your cervix changed that dramatically before your eyes you are at risk for Pre-term labor and delivery. You will need to be watched closely. Depending upon where you are at in the pregnancy, a cervical length of 2.5 cm or less may alert your doctor that you may need a stich in the cervix called a 'cerclage' to keep it closed until 36 weeks.