After coming off birth control, it can take our bodies a good few months to get used to not being on it and so missing and irregular periods are common for a few months.
If you've been sexually active since January then I would take a pregnancy test just to rule out pregnancy. I would see your doctor, they'll be able to look into if anything else is delaying your period and can even give you something to induce your cycle.
did you not have a period in december? have you been sexualy active & think you could be pregnant , someone are really fertile after getting off any birthcontrol. have you experience any pms/prego symptoms?