It gets worse at night because if I remember correctly, something to do with mold spores multiply around 4AM (I start having trouble like clockwork around 2:35am to 4:30am with stuffy nose, slight increased trouble breathing). That's just means from what my allergy specialist said, it's a mold allergy. You might have dust & dust mite allergy too. If you can get a decent allergy cover for your bed & pillow. They make them without that annoying all plastic all over now too. It helps a lot with the dust/dust mite allergy but only if I wash it once a week in as hot of water as possible with a cup of bleach added to the water. I gotta take it easy on the bleach tho... It bugs my lungs.
The only thing so far that helps me with the night time problems (and I have tried a lot, singulair, clarinex-d, claritin, nasacort, allegra -i'm on this now for outside allergies, umm... you name i've probably tried it. Most either give me mild heart beat issues or make my anxiety go up except for the allegra. BUT for sure, my life saver so far for night time & even day time if I get too much fluid in lungs or nasal stuffiness is generic mucinex & generic mucinex with phenylephrine HCI. All mucinex is, is "Guaifenesin". I have some Guaifenesin pills without phenylephrine HCI & another bottle with it. The phenylephrine HCI is a decongestant that does not have any Pseudoephedrine in it (that's what causes the heart issues). My asthma & allergy doc said to take 600mg of guaifenesin every 4 hours as needed. The phenylephrine I only take when I have a stuff nose/swollen nasal passages. Be careful taking this though. If taken regularly can cause blood pressure to go up. It happened to me only once though in a year. That time I was taking it every 4 hrs for 2 days straight which I never do. I take it is my situation is very bad or just right when I need it. It lasts for 4 hrs.
I'm also on azmacort steroid inhaler & xoponex as needed (rarely now).
Good luck & if you need anything, just ask.