My blood type is completely different from my parents. how is this possible? my parents blood type is o+ mine is b+?

Genetics: Ordinarily, two parents both with blood type o cannot have a child with blood type b. There are a few rare ABO alleles, there is the possibility of a lab error, and there is also the possibility that one or both are not your biological parents. Ask each parent separately if you truly want to know and perhaps have trouble -- but decide first whether it's worth it.