Why am I having pain in my breasts since few days, they have also enlarged ever since?

I'm 24 & have an active sex life.. I've been experiencing pain in my breasts for few days now. I have tried to feel any lumps but cant be sure of them. Also their size has increased in few days as though they are swollen. I knw sum women feel breast pain during periods but it never happened to me. I cant figure out wht this is & i'm really worried. I dont hav any one to talk to abt this. Pls help