What could be the reason!!! HELP!

Katie • Momma of 2, TTC #3(:
Since the day after I ovulated which my peak day was the 4th so the 5th I started getting sore breasts, especially on the sides of them is where its the sorest and still today the 9th they are still sore. I take my bra off and they just feel so big and heavy. Its wierd and yesterday and today I have noticed creamy white CM in my panties .what could be the reason? I took a test but it was BFN ): not suppose to get my AF till next week on Friday...I'm going crazy here!(learn more on Glow: https://glowing.com)