If i start birth control on the first day of my period will i continue having my period?

Yes, likely u will: Like most long term medications, the effect takes time and typically requires multiple dose before attaining a steady level for therapeutic effect. Since your menstrual cycle is hormonally regulated, starting ocp on first day of your cycle likely won't affect the current flow at all. But like all med, unexpected reaction can occur and so if you have trouble, consult doc. Good luck.