Bad breath &bad smell in my nose. My boyfriend can tell me what I've ate by the smell coming from nose. I've tried peroxide. What can I do/whats cause?

Deviated septum. You may have a condition known as " deviated septum" that affects normal passage of secretion from your nose and cause stagnation, this way there are billions of odor producing bacteria, that are being retained there and cause this characteristic odor. Please get referral to ENT specialist.
Dental hygiene. I am going to assume you do not have a zenker's diverticulum, a pouch off the esophagus that holds recent food, or achalasia. Try brushing, flossing, and running the floss across your tongue frequently. If this does not help, it's time for a gastroenterologist's workupl.