The peril of testing before you should

Well, this will be a lesson in waiting until your period is due, I suppose...I tested at 12 dpo, 2 days after after my faint positive test on 10dpo. I was, of course, expecting a darker line than 2 days ago to indicate a healthy, progressing pregnancy.  What I got instead was an even fainter line, barely visible, although it did appear within 3 minutes.  I was floored.  Your HCG is supposed to double every 36-48 hours, so this was rubbish.  Breasts were still sore, twangs and pokes still present and that weird feeling of being pregnant.  Funnily enough, face to face with a 'might as well be' negative I started to feel not pregnant.  Let's face it, if you have to hold the test up to the light to be sure, positive it ain't!  My sneezing and runny nose also developed into a fully blown cold, so nothing to do with pregnancy symptoms either. It was obvious that, either the Ovitrelle was still in my system at 10dpo and was leaving it by 12 dpo, or I had a fertilisation that just didn't implant properly, hence the fading positive.  I also got a very upset, churny tummy later that day and lasting all of the next day.  Signs of my body rejecting anything made?  Hmm.  To say I'm not driving myself mental would be a lie.  I am still having hot spells like I did with previous pregnancies, don't have the psycho, ratty behaviour normally present up to 7 days before my period and still feel a bit different to other cycles.  It's remarkable, the power of the mind.  The thing that tells me that I'm not pregnant is that weird, shaky, low blood sugar feeling that I always get just before my period, progesterone or not.  It's here and it's unmistakable.  I will test tomorrow, but I already know the result.  My last fling really, really had me fooled, but it has come to nothing.  I suppose it was just too unlikely.