Can I b pregnant?

I ran into a girl yesterday n she had said she was 6 months pregnant and was going into labor and I was telling her my situation and she told me that she didn't know she was pregnant til like few week prior to that bc she got her period as she always would so pretty much can you get ur period and still b pregnant?????? She said she could pee all day on a stick and never test positive the only way is by blood test by her she said and my mom said it happen to her on her last pregnancy