Pennies - so sorry to hear you are having all these problems. I suspect it may be to do with the accelerated chemo combined with a lowish wbc count to start with, because my experiences were similar to yours.
How far down your throat is the ulcer? When I had ulcers I was advised to wash my mouth out and gargle with soluble aspirin (dissolve 2 in approx half a glass of water). It may give you a little relief. And can you ring out of hours doc. or your unit for advice, they may be able to give you something for the ulcers. (I had adcortisyl tabs., but mine were more in mouth than throat - but definitely worth enquiring)
I sympathise massively - they are awful and depressing, I hope you get some relief soon.
I had loads of the injections - and don't feel as if I suffered any ill effects so try not to worry too much about that. They may also lower the dose temporarily, and then put it back up when you are a bit stronger. Perhaps they will also consider putting you on the three week regime, to give you more recovery time?
Of course you are anxious - that is very natural, - but remember chemo is only one of the ways they are tackling your cancer, you've had surgery, and will be having other anti cancer drugs (and Radio?) Talk your concerns over with the oncologist, they will be able to reassure you. (little tip - write down everything you are worried about, so you don't forget what you want to ask)
This is such a bloody awful business sometimes, it is one step at a time, and try to deal with each bit as it comes. Take care, and hope you fell a little better soon xxxxxx