has anyone got a positive and went to the doctor and got a really faint line even when the tests you took where a darker positive?

i found out that i'm pregnant on december 16 and took 2 tests one came positive with a really faint line and the second one was darker, on december 17 i took 2 more and were clearly positive, made an appointment with planned parenthood to take a tests and it was a clear positive too, but yesterday i went to my doctor and she said that my test was negative so i showed her my tests and she did 3 more and were really faint you could barely see the line, so she asked if i was bleeding or spotting but i'm not i just have cramps and a little pain in my lower back but that's all.

also the tests i took were the ones you can take before your period is due and my period was due yesterday so i took the tests early

my question is should i be worried?