Pregnant or not? if not could something else be wrong?

my friend had unprotected sex on april 23 and he accidentally went inside her. she has missed her last 2 periods but has taken 2 test and both negative. she told her mom and she didnt really care but her mom has 7 kids nad told her that with most she had no symptoms and didnt start showing until around 6 months. has anyone else had a negative test at 2 to 3 months? she is in texas with her mom now but when she gets back she is going into the doctor.