Thanks Lysndan and MissB.

I am almost 100 per cent sure it isn't a problem with progesterone or a LPD. In more than 25 years of having a period I have never had a short cycle (that I can remember!) and my progesterone has always been good.

The blood is definitely in my CM.

MissB, I would love to believe it is implantation but I think it is too early

If anyone has any experience of early implantation bleeds, I am more than happy to be proven wrong