I did a second test and it still says weakly positive I did a scan but the DR said there is no pregnancy but there is syst, can syst be wy it shos pst?

Pregnancy Test. If you are newly pregnant, a scan would not show a intrauterine pregnancy, as it would be way too early. The cyst could be what's called a corpus luteum cyst, which is what sustains a pregnancy until the placenta is formed. The best time to scan for confirmation of a pregnancy is 5-6 weeks, and viability at 8-10 weeks.