What could this be? a week after embryo transfer

I had two 5 day early blastocysts transferred on 22nd August. My test day is this Saturday 2nd September. I have no real symptoms as yet. I just went to the toilet and although there was no discharge when I wiped, there was this small amount in the toilet bowl (sorry for tmi). No blood in it so i wondered if it could be implantation as doesn't it normally have blood in it? Any ideas what this could be?