Positive test then negative?

I had two faint positive pregnancy tests- (not an evap line as it was immediate) now everything is coming up negative. I have been using different tests and testing randomly but even my first morning pee is negative.

I would only be 3 weeks, 4 days.

I’m even lactating, having slight cramping, super nauseous, boobs hurt, all the signs are there!

Could it be that it’s just too early? I am supposed to miss my period next week and I have a dr appt on Wednesday. I’m just super nervous that I’m miscarrying. 😞

Any advice??

Thanks!