K.P.
Ah yes... I asked the same question a year ago. Yes. This happened to me. I was about 8 weeks pregnant, but "measured" closer to 10 weeks. I panicked and posted. Twins run in both of our families and I also Googled it...
Here's what my OBGYN said to me after I called him sobbing...
Measurements are estimates based on averages. Every woman's body is different. Each pregnancy is different. As long as there are no elevations in your blood work and nothing comes up on the ultrasound, don't worry about it.
Everything evened-out in the end. My daughter was a singleton. She was actually quite small. I did not deliver early. He also told me that it's not unusual for this to occur following a c-section b/c of scar tissue and the fact that your uterus never really returns to it's original size. Considering that this is your4th pregnancy... no worries.
Take a breath