Im kinda lost. Im 3 days late. I've taken a home test it was negative. i went to the doctor…

Im kinda lost. Im 3 days late. I've taken a home test it was negative. i went to the doctor yesterday for an unrelated issue and he did a serum test while i was there. Got the results today and I was under 2. I understood a postive result is 24 or higher. A retest needed is at least 5. But I have absolutely no signs of starting my period. I come with a huge list of symptoms. And I'm exhausted by like 3 in the afternoon. Crazy food craving for stuff I have never even remotely liked. upset stomach off and on through the day. I don't understand my being late which never happens and the lack of period signs with the other happenings. Could I be pregnant but not have the levels needed to show postive on a blood serum test? Or is my body just being absolutely crazy?