Hi Londonlottie - nice to see you on this thread and thanks again for introducing me to the other FF site (confusing that there are two). The only reason I'm concerned about a BFN on 8dpo (10 days after hcg shot) is because a few cycles ago I had a suspected early mc and didn't get a negative until 13 days after the shot, so I have a theory in my head that if I'm pg the test won't go negative. There are lots of different strengths of hcg shot and people metabolise (is that a word?) at different rates, so may not mean anything for you though. Also I've read somewhere that a +ve, -ve, +ve after hcg shot means you're pregnant so it must happen for some people.
If you know your usual temps you could start temping now, which would give you the pre-AF warning.
I can never wait until test date either, I usually give in at day -3 when the cb digital is 87% accurate. Even though the bfns are disappointing, I get carried away thinking I'm pg and the early testing brings me back down to earth more gently. I'm still undecided at what's best.
Now you can all tell me off as I know you should never do it, but ... I was in such a rush this morning I didn't look really closely at the test, didn't accurately time the 5 mins (was just counting in my head) and left the wrapper on the windowsill. When I went to put the wrapper in the bin this evening I picked the test back up again (very bad habit I have - there was nothing yucky in the bin - other than the used pg test of course ), but there was a line there. I know one can appear after a while (there's no don't read after time with the test I used - internet cheapie with poor instructions), but I used these tests last month and no line appeared after a negative result then on any of them. So maybe I jumped the gun thinking I had BFN this morning. Of course still could be from the hcg shot so doesn't mean anything and was very faint but pink not grey. I will try not to test again until next Wednesday (but I said that this morning )!
Really hope the IVF worked for you Lottie and good luck everyone else too xx.