Very tender breasts

Rebecca • 17. Getting ready to be on my own. Trying to live the best life I can while battling depression.
So my boobs have hurt so much. It's not like a sharp pain it's like pressure sore pain when I touch them or wear a bra. I wear a 34b and I measured today and every where I looked it said I was now a 34d so that says how swollen they are. But I have no idea why! I'm 17, I'm not pregnant nor am I on my period. Today is the last day of my fertile window, and they've been like this for about four days. Any ideas why?