I am 8 weeks pregnant going off my LMP but today when I got my untrasound the lady infromed me I was 14 weeks... I never missed a period until recently when I found out I was pregnant and I haven't had one this month.. I don't know what to believe... should I just go off my lmp? I am worried...

You go off what your doctor tells you. They have methods for calculating due dates.

It's possible that what you thought was a menstrual period was not actually one. Some women will have spotting and bleeding in early pregnancy, sometimes thinking it is their period.

As J_9 said, various methods are used to date a pregnancy, including ultrasound which looks at what structures are visible in the uterus in early pregnancy as well as baby's size.

After your doctor reviews the results, he/she will order a repeat scan if there is a need for confirmation. A pelvic exam will also give them an idea if the dates are consistent.