anybody experienced implantation bleeding? Need help please

[Laurabub84]

Ok, so my periods aren’t exactly regular. Anything between 32 and 38 days. So I usually ovulate anywhere between cycle days 18 and 25. Today I am cycle day 24. I temp same time everyday and as of yet my chart shows no rise to indicate ovulation has occurred. All opks I have taken have been negative. The last couple of days they had been almost positive so I’ve been hoping the following days would finally be positive but no. Lunchtime today I went to the loo and was surprised when I wiped to find I’m spotting and it’s a strange colour which to my recollection I’ve never had before. It’s brownish in colour, like a light chocolate milkshake colour (sorry tmi) but it’s scared me a little. 1 because I don’t see how it can be my period this early and I never get bleeding of this colour. I’ve had brown bleeding like at the end of my periods but it’s different to this, darker in colour and you can just tell it’s old blood and 2 as far as I’m aware I haven’t ovulated due to opks and temps so I don’t think it can be from that. When I google it I just keep coming up with implantation bleeding but I don’t think that’s possible. I’ve attached my chart to show what I mean. I’m so confused and would really appreciate some advice. Have you ever had implantation bleeding, if so what was it like?