Yeah everhopeful PGS is REALLY bloody expensive
It’s a fresh cycle plus the cost of the PGS (at my clinic it’s £2800 for up to 8 embryos, each additional embryo is something like £300 I think, can’t remember off the top of my head) plus the cost of embryo freezing plus the cost of a FET to transfer
So for me, based on the whacking great meds bills for my 2 cycles (£2k a pop each time), I’d be looking at around £13k for a Fresh+PGS+FET cycle 
Unfortunately it’s not recommended to test our subs bench, as to do so we’d have to thaw them all, biopsy them, refreeze them, and then thaw for transfer. To freeze and thaw twice would be a tremendous strain for the embryos and very likely they might not survive a second thaw. So we've got 4 blasts there that we basically have to play lucky dip with. We could hit the jackpot and first one turns into a baby! Or we could go through 4 failed FET or miscarriages. If I'd had a BFN I don't think I'd be so precious about PGS, but being pregnant until 10 weeks and then finding out my baby had died just slayed me. I can't face going through that again if at all possible. 
I believe it is possible to test day 3 embryos, but there’s not really much point for PGS. As you’re trying to find the euploid (chromosomally normal) ones, leaving to day 5 already self selects the stronger ones - not everything that makes it to blast will be chromosomally normal, but anything that DOESN’T make it to day 5 almost certainly wasn’t. So if you have a lot of embryos then you’d be paying a fortune to test ones that if you’d left them to culture, would have self selected themselves out
It’s only really worth doing PGS if you have enough blasts (Dr Sher recommends 4-8) which is why it may be worth embryo banking as per his recommendation, if you want to do PGS. With fewer than that, the risk that you’ve paid a load of money and ended up with nothing to transfer is greater.
Also I believe that at day 5 the potential of biopsying damaging the embryo is I think smaller - because a couple of cells from a really complex ‘too many cells to be able to count’ structure of a blast, I think may cause less potential damage to the embryo structure than taking one whole cell from an 8-cell structure. I could have that completely wrong however. Also, the biopsy of a blastocyst comes from a couple of cells from the trophectoderm - the outer bit of the blast, the bit that becomes placenta - not, crucially, the bit that becomes baby. Whereas presumably with the 8-cell day 3-er, it’s not distinguished what bits will become what!
I could have got myself mixed up on that last point though
Really really hoping that it’s a good sign that there’s no AF breaking through - your willpower is amazing!!
RE; the GP, yours is a good one if you can get your Cyclogest on the NHS, mine wouldn’t prescribe me either Cyclogest or Progynova as my treatment had been private, so said I needed to get the prescriptions privately from my clinic. At least I asked!!