Am I having heavy implantation bleeding?

Patient: I have had sore breasts for 6 days (which I’ve never experienced, not even during menstration), frequent urination, random dizziness, and I started spotting six days before my expected period with weird prickly cramping. I am currently on my third day of spotting. But the spotting has slightly increased from a smear on toilet paper to a couple of drops in the toilet when I use the restroom, enough for a panty liner but still no use for a pad or tampon. The color of the spotting went from light pink to a reddish brown and hasn’t changed in color or intensity since the second day. What could it be after a negative pregnancy test?