What are the risks if i take birth control pills for my irregular periods?

im 17 , a virgin and its been almost 4 months since my last period my gynecologist put me on birth control ( i start Sunday) abut i heard rumors about women being nauseous, light headed and even lactating! what are the chances that ill run into that? and btw my are like really sore and my , they been like like for a few weeks.