Help!

Hi all I’m hoping to hear I’m just being paranoid and others have had similar situation! I’m 16weeks today and this is my first pregnancy! So night before last I had bad stomach loose bowels but I think that was something I ate.. yesterday at work I had cramps and initially thought it was because I had a funny tummy. Went to the loo and started to get pinkish discharge with the cramps. I was so worried as only had spotting around 7 weeks when straining too hard being constipated. Went up to the hospital and they weren’t too concerned so went home. Through out the night I needed a wee a lot (fun of pregnancy) and still pink discharge/spotting. This morning I called gynaecology who said come in and they’ll do an ultrasound. Fast forward to this morning had the scan baby looked great heartbeat great and couldn’t see where spotting was coming from! Only at the end the lady doing my scan was trying to do a rough measurement but baby was in awkward position. She made a quick comment baby looked at 14 weeks but not to worry as this wasn’t a measurement scan… now I’m worried! How can I be two weeks behind when other scans have always been on date! Messaged my midwife who said she couldn’t do much till 20week scan mid November! Has anyone had a rough measurement done during a scan and it be completely off?!? Any positively would be great thanks! Xxxx