How can i be 6 weeks pregnant and i had sex on the 25 of february ?

Unprotected: if you were fertile in Feb. and had unprotected sexual intercourse at that time or earrlier the dates are consistent. Simply stated: unprotected sexual relations will ultimately lead to pregancy. A transvaginal ultrasound wil be helpful in clarifying baby's size and estimate dates.

Week count: The week count for pregnancy starts on the first day of your last menstrual period. It's a convenient way to count a 40 week pregnancy but odd at the beginning. Typically, the pregnant woman was not pregnant for approximately the first two weeks of the count.

Early pregnancy: estimation of dates can be inaccurate sometimes. It's usually +/- 7-10 days. Feb 25 was 5 weeks ago, so 6 weeks is within the margin of error of the tools we have available to estimate early gestational age. Thanks for trusting HealthTap!