4 weeks pregnant maybe?

I'm writing this with a lot of anxiety, but a little hope as well. This morning I've had my very first faint lines on my pregnancy tests, according to the app I should be 17 DPO. Have been spotting since 12 DPO lightly but thought AF is due to come. It hasn't, so I was lucky to find an appointment to my doc today, and had an ultrasound and took blood to see HCG levels and Progesterone. The ultrasound showed a 2 mm spot in the uterus but doesn't really confirm anything, however the doc is hopeful. I don't know if I should get my hopes up and the spotting scares me a lot. Any positive experiences? Thank you!

Update: HCG level came back low, only 13 mUI/mL, doc said it's either very early pregnancy or my AF will come soon, the 48h later HCG should clear things out. I've never heard of such low value, so I pretty much lost my hope.