I had irregular periods and couldn't base my due date on that, then my first ultrasound was in January 31 and in the sonogram it showed I was 18 weeks 3 days, the second ultrasound was in March 4 and show I was 20 weeks exactly, now I am confuse and don't know when I'm supposed to be due,I'm worry because I have had 2 induce pregnancies and there's a 4-5 week difference.