Bug, I know you must be having bittersweet emotions right now, but rest assured you're doing your best for your baby and of course for yourself - you need to be healthy for Iain and for the new baby.
I do understand the financial burden though. I'm self employed and luckily 80% of our income comes from my husband's job, but my 20% still helps. In the past month or so I've become slower (my job is manual to a big extent - I make and sell clothes - but being a one person business I also do everything else, from marketing to finance), so I've started to turn some business away, as it's taking me longer to finish stuff that would normally be much quicker to do. And it's only going to get worse. My plan as of now is to stop working all together around the time I hit week 36 and devote the first few months of baby's life to being a full time mom. Then at some point ease back into work, but only as part time. It may not be for a year or longer that I return to full time work. This is the plan, however, given how much harder some things are already becoming for me to do, I've wondered a few times if I might be forced to stop earlier than planned, so we'll have to see how things go. This will definitely put a financial burden on the family budget, especially with the added expenses of a new baby, but luckily, we are expecting a raise from DH's job to kick in next month. So at least that should give us some breathing room and somewhat offset what we'll be losing from my reduced work.