I just wanted to give a quick update in case anyone is reading this thread with the same issues, and also to thank you all for your comments - they really helped.
I'm not halfway through week 5 and, until yesterday I was struggling to get more than 200 calories a day. I've lost 32lbs in five weeks - so that's been amazing - but, for the first time in my life, I started to worry about malnutrition. My skin has started to show the effects of so little nutrients.
Anyway, I had a bit of a breakthrough yesterday. My doctor had told me that as long as my calories were Protein, that was the most important thing. So I stuck to trying to eat eggs, chicken etc, and could manage about two tablespoons, or less, and I would start feeling so nauseous I had to stop.
Anyway, yesterday I was feeling so ill that I decided I didn't care what I ate anymore as long as it had calories, and I bought a tuna mayonnaise sandwich on soft wholemeal bread, and some pate and bread. Turns out, I can eat these (without crust). I ate almost the whole sandwich! Amazing. Took me an hour, but whatever. Anyway, I think the carbs are helping the protein go down or something. Saying that, I tried Pasta a few days ago and that didn't work at all. But I feel like a different person today. So far, I'm at 200 calories for Breakfast and lunch - which doesn't sound a lot, but compared to the last few weeks, it's a huge change.
I'm seeing the doctor for my follow-up on Monday, so I guess I'll find out more then.
Thanks again for all your comments