What could be mimicking pregnancy symptoms?

My friend had a postive pregnancy test a while back but her bloods came back negative. Also some negative pregnancy tests. Since then she's had strong pregnancy symptoms, even movements in her tummy. She's even getting faint lines and negative lines on some tests at the same time. (Many weeks after finding out she is pregnant). I'm sure you cannot get a false positive test?? The drs felt her stomach and said they can't feel anything. But she's still getting faint lines? What else could be mimicking these symptoms? Could she still be pregnant??