can pregnancy cause you to react different to medicines?

Bailea
I used to take this one allergy pill every day(my allergies are terrible)! The past two times that I've taken it, within the last week, I got dizzy and I would feel like my speech was slurred! I almost felt like I had a few drinks. It never made me feel like this before. Any idea why it's doing this? I haven't taken a pregnancy test in about a month or two.