I'm wondering something that is just confusing me so bad and no doctor will help me with, so my periods have always been off, until about June of last year. Then they came pretty consistently on the 29th of every month until I had sex on October 14th and 22nd of last year and missed my period for that month. But about 2 weeks after the 22nd I had an almost period like bleeding for a day. Was that implantation?? I had found out I was pregnant sometime in early Dec. and I was about 5 weeks then when I went in for my ultrasound Dec. 20th of 2017 they said I was 6 weeks and 4 days along, I have had a couple different due dates and my very recent one is August 5th of 2018. I went in Wednesday for an ultrasound and came out with being 29 weeks and 3 days pregnant. I am exactly 30 weeks today. So basically my question is, how many days/weeks can an ultrasound be off?? Especially because my last period was September 29th of last year!! Someone please help, it's driving me crazy!! Lol