@cardboard33 Thank you so much for your advice. I'm not really talking to anyone about it - sounds ridiculous, but I just haven't had time. I spoke to my husband about it properly for the first time yesterday. I haven't got a Macmillan nurse, but I have been assigned a genetic counsellor on the NHS, who has said I can contact her whenever. I don't really know what I would talk about though - it's all just theoretical at the moment and I am torn between wanting to think/talk it through, and not wanting to waste time worrying about something that may not even come to pass!
I had quite bad post-natal anxiety after my son was born and I am a little bit worried that if I have an unwelcome result with this genetic test, I will go into a black hole of worrying once all the post-birth hormones are swishing around. On the other hand, I think I might end up in that hole anyway if I don't find out one way or the other, and at least if I find out then I am on the way to doing something. If it is bad news, I need to be strong in the way that I deal with it. I think probably I need to spend the next few weeks preparing myself for bad news and getting myself into a positive mindset to receive that news. I don't think that would be a waste of time.
Regarding the bump size, I've had a couple of people ask if I'm due soon! I'm like... no... in three months' time!!!!! I think because I'm short and small (and I've popped out quickly as it's my second) the bump just looks ridiculously big. I'd say the little football was definitely a compliment. Beach ball over here 
@Angelmiracle sounds like a great appointment. Well done on the weight, too - that must be a relief!
@AssumeItWasSomethingClever ooo it would be a shame if you can't get away with the extra pay - that sounds ideal. Although if you find you can't take the work, at least you can just enjoy being with your little one, guilt-free!