It's possible if you ovulated late... however, I don't wish to scare you but based on my first pregnancy, I was also measuring about a week late and that pregnancy wasn't viable as I started spotting early around 7 weeks which then ended nearing 12 weeks. If you feel concerned about your baby's health, there's no harm in asking for a second opinion from a different doctor. Wish you all the best
it could happen if your period is irregular so don't worry so much yea