I searched the Web and I came across this article explaining the meaning of B.D it says that B.D means twice a day but it doesn't specifies that I have to take the medicine twice a day before or after meal, I mean after/before breakfast and dinner?
As @LangLangC pointed out, bis in die is Latin for twice a day.
However, usually drugs come with a prescription information a bit more elaborate, and twice a day is more commonly abbreviated as B.I.D.
This example and further examples can be found here.
In this example, p.o. (per os, latin for through the mouth) means oral consumption, and b.i.d (bis in dies, twice a day) twice daily. It is not specified if the intake should be before meal (a.c. or ante cibum) or after meal (p.c. or post cibum).
Your pharmacist should have provided you with more information about intake when you received your drugs.
You can find a list of medical abbreviations for prescriptions here.