Texting MIL - 17 weeks

I text mil and told her I was 17w today. She asked how I was doing and I replied, having a lot of stretching pains.

She replied with "oh lol are you sure there's only one?" -Side note: her last two kids were twins. So..that kinda scares me because I really don't know. I don't get another U/S til I'm 20-22w. I've only had one at 9w. The tech swore up and down that it was only one. But...I'm still not 100% trusting it til I see a current U/S and they check thoroughly.