Help! Terrible allergy to something and it's making me miserable

I'm 4 months pregnant with my 2nd child and in the past month I've become increasingly itchy. It's mostly on arms, neck, ears and worst of all my face. My face is red and hot and I'm miserable. I've changed everything I use on my face to a sensitive formula. I even invested in mega expensive make up for sensitive skin and I'm still miserable. I've read women can be allergic to their prenatal pills. Has anyone else experienced this?