Nervous & scared

According to the app, I am 6w2d. I had some brown spotting Wednesday afternoon but wasn't too concerned. It was still happening yesterday so I called the doctor. I went in yesterday afternoon & had blood drawn & got a Rhogam shot. They called today & said I'm 4 weeks based on the blood work. The spotting is also getting heavier & more reddish/pink. I go Monday for more blood work & an ultrasound but I'm so scared. This is my 2nd pregnancy & nothing like my first. Any advice? I also am confused that the dates are so different for how far along I am.