Spotting, implantation bleeding or another period???

Hoping someone can help. Ttc baby #2 and recently came off bc but had strange bleeding mid cycle. Dates are:

4-7 Jan = period

15-16 Jan = dark red/brown blood. Heavier than spotting as needed tampons both days but only a used a couple (didn't need to change every hour)

16 Jan = stopped pill (cerazette) so bleeding not withdrawal bleed

16/17/19 Jan = had sex, ovulation predicted 17/18

27 = BFN on hpt

1st Feb = AF due

Bleeding was before coming off the mini pill and before sex so really confused. I've still not had any withdrawal bleeding either.

Fell pregnant within 2 weeks of coming off the pill with my first pregnancy so hoping it's just as quick this time!! but the bleeding is worrying me. If it's ovulation bleeding then I might be out this month 😥😥

Help!