I only had one drop of implantation bleeding last pregnancy. i had two days of pink and brown spotting 4 days positive opk. sign of twins? or?

Unclear: If I understand what you are saying you had some irregular spotting after an ovulation kit tested positive. The only way to know if this is implantation bleeding is to wait and see if you are pregnant by taking a pregnancy test if you miss your cycle. If negative then this is just irregular spotting. None of these symptoms suggest twins.