Reasons for sore breasts

Aaron • 23 years old. Married my best friend in October 2015! Not TTC until after I finish schools
Anyone know if there could be a reason my breasts are sore?? 
I'm definitely not pregnant (haven't been sexually active in over a year). Also I'm not ovulating and my period doesn't start for another week and half. Anyone know what could be the reason they are? I would appreciate any help!