Tender breasts??

my boobs are pretty sore right now and I'm not sure what the cause is? I took monistat last week because I had a yeast infection but I don't think that'd cause tender breasts. Im sexually active but I'm on birth control and I take it at the same time every day. Could it be they're just growing? do they get sore when they grow? I forget, I'm 16 and my chest is about a C cup right now.