My girlfriend says that she's 14 weeks pregnant. And I did the math and the week she was souppose to be pregnant she had a misscarraige. Is she lying to me? I didn't think a pregnancy could happen so soon after a miscarrage

At least after 3months.

Pretty soon. I say this because my wife went to the hospital to find out why she was bleeding so much. They told her she miscarried, but also that she was pregnant with another baby. I hope this helps answer your question