Miserable boobs! πŸ˜–πŸ˜©

Mareike
For the last few weeks I've had light breast soreness/sensitivity like I usually always got when I was starting my period. 
This week tho, my boobs hurt so bad I'm literally laying in bed with ice packs over my boobs. They are swollen, heavy, and hurt worse than they ever have before! No lumps or anything obviously abnormal. 
What could this be?! I'm on the Nexplanon since December, after a year of no birth control (this is my second time on Nexplanon). 
Any tips to help with the breast pain or any ideas as to why they are hurting Sooo badly?!