I have tried all otc antihistamines and they all make me dizzy with delirium. would xyzal (levocetirizine) be a good one to try or would it most likely do the same?

Same class: Although there could be some differences between the antihistamines especially between the 1st generation (sedating) and 2nd generation (non-sedating), you may have the same experience on Xyzal (levocetirizine) if you couldn't tolerate Zyrtec, Claritin or Allegra.

Careful w OTC meds: Because you have Gilbert's disease your liver may not process well some medications, so they can accumulate and cause adverse and side effects. Talk w your Doctor he should be able to tell you which you can use. Also thyroid medications (you have Hypothyroidism) can affect antihistamines and other medications, especially OTC cold meds with a decongestant which many times comes in allergy meds.

Same: It may cause the same side effects. Your reaction is not life threatening, however, so it may be worth trying, provided that you don't drive afterward or put yourself in any dangerous situations. Hope this helps!

Allergy treatments: If you have tried literally all over-the-counter antihistamines including benadryl, (diphenhydramine) claritin, tavist, zyrtec, Allegra, Walfinate(chlortremiton), ... Have you tried a nasal steroid spray or nasal antihistamine or nasal chromolyn? Trying prescription antihistamines like Xyzal, a refined form related to Zyrtec, might help. Allergy testing with an Allergy/Immuno dr skin test off antihistamines done?

Probably less: It depends on which ones you have used. Benadryl (diphenhydramine) definitely makes you drowsy. Claritin shouldn't if you have used this. If not, then xyzal would probably worth a try.

Probably: You can try it but if Zyrtec affects you like that, Xyzal (levocetirizine) will probably do the same since they are nearly identical. Sounds like you need to control allergy symptoms in other ways. You can get triamcinolone and cromolyn nasal sprays without a prescription. You can also get antihistamine nasal spray by prescription, that should have fewer side effects than pills.