Thanks for the query.
According to your history and as per the scan it can be said that most probably your boy friend is the father of your baby.
Spotting could be because of causes like:
Hypomenorrhea: scanty flow during periods it can occur due to causes like anemia
Post coital tear: it can present with spotting till the healing of the wound.
As it is almost clear that the father is your boy friend only, you don't take tension about it and be peaceful which is needed in pregnancy