Both the blood and urine pregnancy tests look for the same pregnancy hormone in the body. The major difference between the blood and urine pregnancy tests, therefore, is that the blood pregnancy test is a bit more sensitive, and it will detect a pregnancy several days earlier than a urine pregnancy test will.
One the fertilized egg implants in the uterus, the hormone that the pregnancy test looks for begins to accumulate in the woman's body. The blood test will detect this hormone usually just a couple of days after implantation
has occured, or within about 10 days after having sex and getting pregnant. The urine test, on the other had, lags by several days and is usually not positive until after two weeks.
Therefore, since you are suspecting that you might be pregnant, and you are right on the edge of the time when the pregnancy test in the urine might be positive, you could consider a blood test. In order to get a blood test for pregnancy, you would have to make an appointment with your primary care doctor
or with your OB GYN doctor, who would ask you questions about your last period and your symptoms and then determine whether this is an appropriate test to perform.