Could I still be pregnant?

i would keep getting checked..neither blood (had 6) nor urine tests(took about 27) came back positive in my first pregnancy when i finally had a pos urine home test and went in the next morning for a blood test they thought i was having twins..mind you i had just had abloodd test 3 days prior....anyhow they did my ultrasound and found out uhh no not twins just that i was 3 mo along.....