So confused!

So I started spotting brown discharge/pink on October 5th-10th literally only in the morning.

October 11th I noticed it was just a bit more than the previous days but only pink. Took a test on October 10th and was BFN Took another test on the 15th and was BFN again!

I haven't been stressed nothing has changed. Typically my flo is really heavy do about 3 days, first day is light than 2,3,4 is heavy with clots than by the 5th day its totally gone. This month it's totally weird. Really light cramps since the 5th but no full on period. Just need some thoughts. Been ttc for 2 1/2 years now and no luck hoping this could be it but idk. My 3 other children those pregnancies It didn't show up positive till 5+ weeks. Could this be a sign of implantation?