Possible to have symptoms but BFN & Still be pregnant?

So I am currently 7/8 DPO, tested yesterday & sure I had a faint positive which is apparently impossible?

I tested again this morning and sure its a Bfn but these are the symptoms I have, anyone experienced these & got their BFP??? ...

Cramps on/off the past 2 days & still have this morning

Headache for the past 2 to 3 days only a mild one

Really tired

Temp is still rising currently highest its been at 98.03

Then yesterday and still today im really bunged up as in a stuffy nose/sneezing alot

Help a girl out im going out my mind, I just FEEL different!