I don't know what's happening for sure, but I would switch H1 (and H2 blocker, if needed), one at a time.  Zyrtec might work as an H1 blocker and Pepcid, 20 mg. as an H2 blocker.  Or, you can try each of your current meds at a lower dose and see if that helps.

One thing came to mind, in that the quercetin has stopped working, and that is whether the H2 blocker is too strong and you don't have enough stomach acid to break down the capsule and for absorbing the quercetin.  You could try just using an evening dose of the H2 blocker and take the quercetin in the morning  or you can take the quercetin 2 hours before you try to take the H2 blocker in the morning.

Do ask your doctor first, before changing any Rx meds.

when I first started the H1 and H2 histamine blockers I felt awful. I had too experiment with all the different ones I finally found that xyzal is the best for me along with zantac, I also found if I took a low dose of my H1 blocker in the beginning it was like all the bad symptoms seemed to flare a couple of hours after I took it, so I just had too up the medications and keep sampling different ones. Interesting the Quercetin helped you I took it for a while but I felt sicker on it and actually my Dr. told me too stop taking it said there was not enough research into its use and did believe it helped so I stopped taking it, I think its great it has helped you taking natural thing I think is so much better for you