Hi; I had no idea you were in this situation; welcome to the club! You posted about bad morning sickness, but I saw nothing about reflux or Nexium!
Anyway, while I doubt it's really bad, I would heed the doctors' precautions. They are just being cautious with something that really has no history with pregnancy (like so many other things).
I guess since you'd been TTC for some 1.5 years, you've been off Nexium a long time. I was very slowly weaning myself off it while TTC when I found I was pregnant. I was at the point of 1 every 4 or 5 days - LOL, pretty pathetically scared, huh? When I found out July 4, I simply stopped the Nexium altogether at that point.
I've had a rather rough pregnancy. I've suffered bad reflux and bloating (aggravating my gastroparesis) since about week 5, never mind the things I never had before, such as the dreaded gag feeling. And months later, I'm still like that (even worse in many ways).
I just have to put up with it. Except my gastroenterologist did allow me to continue my 300mg Zantac per day (obstetrician is OK with that too).
Early on I tried various medicinal methods my OB prescribed for "nausea" and all the other gastro irritations of pregnancy, really to no avail. I gave up and just put up with it. 1 has to know that a form of gastroparesis tends to strike when we're pregnant, and it is also possible the lower sphincter weakens, all because of heavy progesterone when pregnant.
I hope that when baby comes, I'll soon be feeling much better! But I'm scared, exactly because I already had pre-existing gastro issues and worry I'm either making them worse permanently, or I coincidentally have gotten worse while pregnant - and on no Nexium or any PPI!