Missed period, neg preg test

Dina • Sun, Nov 30 • 36 mother of 5 boys 20 & 18, twin boys in heaven, would be 4 years old now, and our rainbow baby Cooper Daniel due 7/25

I'm 35 and recently had my tubes untied, my husband and I were intament during my fertile days and I'm now 14 days late but all my preg test even blood test show neg. could I still be pregnant? Has anyone else ever had this happen or know someone who has and was pregnant? Any advise would be appreciated!