Spotting

I have been ttc. My cycles are irregular. My last period was just over a momth ago. I had very light intermittent spotting Friday December 28 that lasted 24 hours. Today is Tuesday Jan 1, this morning i started having light pink bleeding (not enough to fill a liner). It is now night time and The bleeding has tapered off to spotting. The spotting has also been accompanied with intermittent dull aching in lower abdomen and back. I've had bfn's so i am trying to figure out if this is implantation bleeding or my period attempting to start.