Periods or implantation

Icey

My last period was from 23 dec. To 29 dec. I have average 28 day cycle.

22 Jan. night I had very mild brownish spotting.

23 Jan. Mild brownish spotting

24 Jan. No spotting

25 Jan. Morning two three reddish sticky threads.

No proper period yet.

What is it.

PS. I did pregnancy test on 21 Jan and it was negative.

The picture is of 23 Jan.

Please help me, what is it..period or pregnancy..