Hi Aunt Issy,
Welcome to HealingWell!
I can't really help you here, as I have never been pregnant. I just wanted to wish you a warm welcome and to say HANG IN THERE. I've seen a few moms come through here that have said their IBS got worse, and some say it got better when they were pregnant. Like your nurse friend mentioned, it's all hormonal. Maybe, just maybe, you'll get past the dreaded 3 month mark, do a total 180, and feel even better than before.
Hopefully someone else will come along who has actually been pregnant...
Take care and good luck!