Bbt help!!

Shaye • Married to my best friend of 15 years! Married 5 years total! TTC after ectopic #2
I've been trying to bbt and I think I'm all confused... 
​ im a mouth breather and on top of being a nurse I know you can't take an accurate temp orally and get correct results 
​I've been temping under my arm and some mornings I wake up hotter than others lol so idk if that makes a difference either... 
​R u supposed to do it same time every morning and what if u hve to wake up before and use the restroom? I'm so lost I feel hopeless lol