Hi! Constipation can definitely affect both body odor and breath. But unless you can detect the odor coming off from your skin (or used clothes) most likely the source of the smell is your breath alone. That would explain why you can smell it in your mask and around your lower face.
When bad breath isn't caused by the mouth or throat (like tonsil stones), it can come from the stomach & if your bowels aren't eliminating fast enough, it can make your breath smell faecal. It can come from sinus issues like post nasal drip or stomach like GERD.
Begin taking soluble fiber supplement like Metamucil. Drink 2 litres of water everyday (this is = 4 bottles of water) or else it won't work. If you currently have an impaction/mass of old dry stool you may need to take a laxative first.
you are not drinking enough water.
Take chewable Chlorophyll. Take it every day. Or even chlorophyll shakes. Try going off dairy and see if that helps. Your skin and bowels may improve.
You could use goats milk or coconut milk or oat milk instead.
If you don’t see a big improvement in a few months ago off gluten also. You may want to get some allergy testing done if you don’t see improvements after this.
Chlorophyll will help detox and clean that smell odor up.