Hard to breath


I’m 9 weeks and 4 days pregnant according to this app and I’m finding it very different to breath through my nose as I usually do I feel like I’m not getting enough oxygen so I’m breathing in and out through my mouth but I’m breathing very heavily now I don’t know if this is normal I don’t think the heat is helping very much but I’m the same once it’s cooled down as well? Anyone have any advise? Xx