advice please

Libby • Hi :)
Can someone clear this up for me im very confused.  Im getting nauseous,pelvic pain,tender breasts. My doctor wont test for pregnancy till about Wednesday. I have had one very very very faint line on a test then the rest are negative i even took a clearblue Digital test and that said not pregnant.   Is there a possibility that I am  pregnant and my levels are not high enough for the tests. Or is all these symptoms just something like else.