Suggest Treatment For Irregular Periods?

hello my name is riya my height is 5 "4 and my age is 20,
i have a query that my periods are not regular, it comes on irregular basis like 30 days, 45 days etc but i never missed my periods and also when periods come than for first two days it take lots of pain that i could not bear i cannot move a single step, and it is happening from past 8 years, so i went to doctor and she gave me medicene named pyridoxine and told me to take it for 7 days before periods mean to say when i feel like having periods than before 7 days from period starts i have to take daily 100 mg b long tablet.... Named pyridoxine so i took it as i was told in the month of nov. And period came on 29th nov. And also i am engaged so i had sexual intercourse with my partner on 27th nov and 28th december using condem precaution my last period got end on 5 th december so today is 17th january and i have not got my period yet..
Please suggest me what should i do now.. is that delay is because of pyridoxine tablet or any other reason?