You can consider a humidifier. I had really bad nose block during pregnancy. I used a diffuser from muji and put essential oils like peppermint in it to help me sleep better. For blocked nose, I also used warm compress on my face. I used the warming eye mask from Watsons. https://www.watsons.com.sg/steam-eye-mask-rose-fragrance/p/BP_70110 If you really want to take medication to help with the itch and blocked nose, chlorpheniramine is safer than decongestants like telfast or zyrtec. I've checked with a GP before and read up on drug safety on my own.
Try Neilmed nasal saline rinse? Use it to rinse your nose before sleep. I have the same issue, and mine is bcos of allergic rhinitis. The itchy throat is bcos of mucus back flow from nose to throat. So as long as you clear the nose, the throat should be fine.
I am facing this problem in 39 weeks, would suggest to use a fan instead of an Aircon. keep room clean and take hot water bath. try breathing techniques that will help alot
Do you sleep in an aircon room?
Cherlyn