5 weeks and sinuses are out of control

ugh how long have you been dealing with it?

I don't have any advice for you other than what my allergist told me - Zyrtec is a category B drug. Only category A drugs are known to be totally safe for pregnant women, in that they've been around for a long time and several studies have shown them to not cause any harm to mother and baby. Any drug outside of category A only increases the risk. B somewhat risky, C very risky, D incredibly risky etc. While Zyrtec occasionally is fine, it's not always the best choice. You can check with your ob to get their opinion as well and also their suggested alternatives. It sounds like you're already doing everything you can. If you weren't already aware, propping your head up at an angle when sleeping is a good way to stop post nasal drip. Also sinus rinse 1-2 times per day or as needed but not too close to bed time..
I hope you feel better soon