Is there any possible way a blood test would come back negative?

Hi everyone! I'd been having unusual symptoms the past few weeks (mood swings, sore boobs/nips, have to pee all the time, couple pd days late, etc) so I decided to take a test. It was positive and I'm happy but I'm not sure if I can be thrilled until I get the blood test. Earlier this year I took a test that came back positive and I couldn't get to the dr right away. For a full month, we thought we were pregnant until we finally went to the dr for the blood test. We were crushed to find out it had been a false positive. I took 5 tests this time to be 100% sure but I still have my doubts. Is there a way 5 tests can be wrong?