Sounds like you've made a lot of really good changes. Sorry to hear you've got issues. Looks like constipation is a side effect of both zirtec and zantac.
What kind of fiber are you getting in your diet? Lots of fruit would be good for constipation.
I think the yogurt thing is great. You might consider a small of amount, like a spoonful, of yogurt with each meal.
I'm guessing you're fighting your medications, that they're causing your constipation. You might look into the "methylation" process in human bodies and how that relates to histamines (and thus anaphylaxis). Try identifying whether or not you're an undermethylator (and histadelic), and try improving your methylation if it seems to be the issue.