Implantation or normal period.?

So on the 15th i took a hpt bc my boobs were extremely sensitive more than usual and cramping more, however it was neg. my period was due on the 18th but I started spotting on the 17th exactly 12 days after ovulation. It has been very light pinkish except for the 18th it was a medium but light red flow and the 17th i was lightly spotting and slight cramping, which ik is normal. on the 19th it was extremely light to non existent with some brown discharge and has been stopping and starting off and on for 5 days now. I've also been having terrible back pain, major acid reflux, hot and cold flashes, and a flutter like cramp in my lower abdomen. My cycle usually last 5 days and is pretty heavy with major cramps but always consistent , could this have been implementation bleeding or a normal period.?