Confused

Heather

Ok so I always have pretty regular periods. I also never skip or miss a period. I also do not have PCOS or endo. Well I am now late for my period by 5/7 days and if I was pregnant I would be 4 weeks. Well I took a urine and a blood test at the hospital when I would have been 3 weeks if pregnant. They both came back negative. I guess what I am asking is could it be too early for it to have shown positive?