Hi. Iv been hoping to conceive and I had unprotected sex on 24th October. Yesterday 2nd November I had some slight pink coloured blood which has happened again today and some very slight cramps in my tummy. I was wondering if this could possibly be implantation bleeding or could it just be the start of an impending period? Its just that normally if I was going to come on my period Im pretty certain this would have happened today. How long after unprotected sex would implantation bleeding occur? Iv also been having some very mild back ache in the base of my back too. Can anyone advise me? Please? Thank you in advance.