Diclegis and Zyrtec

Ok ladies my doctor prescribed me Diclegis today because my nausea is so bad I can't even get out of bed without throwing up. So I am starting it tonight. I have been taking Zyrtec for bad allergies and I'm wondering if I should stop taking that now since the Diclegis is an antihistamine. Has anyone taken both? I'm worried if I stop the Zyrtec my allergies will get even worse. I am allergic to damn near everything.