Hi I had my last period at may 5 and ended on may 9, I had intercourse with my husband at June 1 to June 30 because he works in the other country.
I got my first ultra sound on July 8 and it says I'm pregnant for 7 weeks and 4 days?how is that possible that I get conceive at the month of may without having sex with anyone?
Now its my due month and my oby said that I'm getting over due at the 3rd week of feb.

Pregnancy is calculated by the first day of your LMP (last monthly period), which should give you a due date of around February 9. Calculating pregnancy is an inexact science that cannot take into account fluctuations of ovulation for every woman who becomes pregnant, therefore, using the LMP is one of the more reliable methods.

Considering paternity is not in question, it appears you may have ovulated later than what might be usual for you.

There is no way to determine exactly when conception happened.
No you can not get pregnant, unless there is sex involved.

Dates of conception are based off information you give the doctor and from comparison of averages.