Last period is around end of may and Urine pregnancy test on July 3rd was negative but two urine test at doctor's office on July 10th is positive ultrasound on July 15th can't see anything why?

Hello, I'm sure you're going crazy right now. The same thing happened to my husband and I and after having an ultrasound several weeks later, everything was fine. All there is at this point in your pregnancy is the sac and often times the fetus can not be seen for another week or two. Your doctor may opt to have you take Hcg blood tests to ensure your levels are rising (rules out an ectopic pregnancy in most cases). Be patient, amazing things are happening in your body. If you have spotting or bleeding then call your doctor immediately.