Hello,cThank you for asking your query at DoctorSpring.
From your symptoms it implies you are suffering from abortion of ectopic pregnancy.
Ectopic pregnancy, is when fertilization occurs elsewhere other than uterus, that is the fetus is present elsewhere other than uterus. Sometimes urine pregnancy test comes negative, due to false positives. I suggest you do a urine pregnancy test yourself and confirm once again.
Since you are having period for four weeks, there are high chances you may develop anemia. Therefore, take iron tablets once a day. Do a blood test, where you ask for hcg, hcg level increases during pregnancy in blood. Repeat USG, ask for radiologist to look in for signs of abortive ectopic pregnancy.
the abortus has to be completely removed, as remains of abortus can lead to severe complications like excessive bleeding etc
Hope this helps. Please feel free to ask follow-up questions