Pregnancy tests are not always accurate

My friend who is studying to be a nurse thinks i may be pregnant even though i tested and came negative. I don't blame her she has two daughters and all the symptoms i been describing her sounds like pregnancy even my belly looks. If i am i may be 2 or 3 months. My boobs won't stop itching and i been having cravings and fatigue. Low back pain and nausea. My skin on my face has got clear and with acne not only on my face but also now back and chest. Theres more symptoms but im making a doctor appointment to make sure. I took my test by peeing on a cup. Party plastic cups. So she says it would of been better if i had peed on the stick.

Anyone ever had a false negative?