Faint Positives. Missed Period


I need help ladies. So my period is now 4 days late but I went to the hospital when I were a day late and told them I had stomach cramps and lower back pain. They did a urine test (negative), blood test (negative- less than 2), & a ultrasound and I’m guessing it didn’t show anything cause they didn’t talk to me about it but I’ve been getting faint positive pregnancy test at home. Is it possible I could be pregnant and it was just too early for them to tell at the hospital?