Ok beanie, sorry very much to obsess on your behalf, but:
'I've been getting highs for two weeks though, and the monitor gives a peak after a few highs normally. It's not a sudden leap from low to high unfortunately. I know the highs come from an Estrogen increase and the peak from the LH increase so am assuming as there was no peak I didn't ovulate so didn't get the LH surge you see when you ovulate.
naw--here is my theory: the second line doesn't show estrogen (though its raising in your body), it only shows the raise of LH or hcg if its there. If it isn't low long enough first, the monitor calibrates the peak line to be 'high' and waits for something stronger, which will never come as line is already maxed out.
If it didn't go low-high but was high for two weeks I guess you are pregnant from last cycle and that bleeding wasn't AF.
'My last period was slightly different to the last few in that it stopped and started and I got spotting about 2 days after it had stopped.'
Aha! My gynae said that implantation can look like period and then some. If it's weirdly different from af, so much the better I say.
' I doubt this was implantation as it was before I usually ovulate.'
Hu? Bleeding before you usually ovulate? That doesn't excldue implantation! Especially if you don't ovulate when you are already pregnant.
Tadaaa! Not to get your hopes up hun, but I'll eat my hat.....