measuring bigger then 28 weeks

Carlita • Wife 💍& Mom of 👧🏽👧🏽👦🏽. Expecting🌈👶 2/11

So last week I had my check up . The midwife listen to her heart rate and then measured my belly. She adv me that I'm measuring a few weeks ahead. Now I'm 29 weeks and wondering if I'm even 29 weeks or am I 30 or 31. My midwife adv she will order an ultrasound at 36 weeks but I'm thinking that's to late since my due date may be off.