Almost two weeks late, faint positives on multiple hpt, had an ultrasound this morning and nothing came up,

They said they havent yet ruled out early pregnancy and need to get blood results to confirm and then a follow up blood and ultrasound!

I then went to my dr this afternoon and she said my bloods were negative BUT asked me to come back in, in 2 weeks and she also said if I was to experience any pain during that 2 weeks that I am to head straight to the dr!

If it wasn’t a pregnancy or what they think might be, why are they asking me to go straight back in if I experience pains and why a follow up?

I’m going crazy☹️