Weird breathing patter help please?

For a while now I have had a kind of unusual breathing pattern. Essentially if I breathe for more than like 5 mins through my nose, it feels like I am not getting enough oxygen and I need to start mouth breathing for a couple mins until I catch my breath again. It also feels like there is way too much mucus in my mouth/throat, which makes it feel like I am choking sometimes. I went to an ent recently and discovered that I have a deviated septum and some allergies, could this be a contributing factor to my condition? My nose always feels somewhat congested, and even in the rare moments that it is clear, I still cant breathe too good through the right side of my nose. Whyat could be causing this weird breathing and what canh I do to fix it?