Hi,
Thanks for the query.
Changes in the menstrual flow can occur due to many causes like
hormonal imbalance, thyroid abnormalities, weight changes, anemia etc.
As you had complete 4 days period, the possibility of
pregnancy is less.
And yes, sometimes urine pregnancy test kit may not detect early pregnancy.
But just by that we cannot come to one conclusion regarding
miscarriage.
So, if you want to confirm, once go for
blood test for pregnancy.
Blood test for pregnancy measures
beta hcg levels.
Which will be elevated in pregnancy.
The levels will take some time to come to zero level even after miscarriage.
So, by doing this test you can detect the possible miscarriage.
Take care.