Thanks for the query.
Sometimes urine pregnancy
test kits may not detect early pregnancy.
But as your blood test
is positive for pregnancy we have to consider this result.
Some amount of spotting can be seen in early pregnancy because of causes like,
embedding into uterine wall.
Some women may have bleeding on expected day of periods even in pregnancy.
Increased blood supply to local organs can cause spotting even on mild friction.
If your spotting increases or pain arises consult your doctor immediately as it can lead to miscarriage