Oh my goodness, losing a baby at 20 weeks would make anyone a nervous wreck the next time around. VERY sorry for your loss hon. That's a big one!!
I'm glad all looks great with this baby. I wish you a happy, easy, successful delivery!
Anxiety in general but around what you eat my be triggered by the loss and exacerbated by the hormones. Talk to your doctor about how you are feeling. They'll want to keep an eye on that because of the issue of post partum being something that can happen. Also, keep a little journal to see if there is any pattern to the worry and also as a place to vent out your fears and anxiety. Then you can imagine that when you close the journal, you are turning off the anxiety. Visualization can be powerful.
Anyway, keep your doctor in the loop about these feelings and hang in there. peace