Hi Sheila! Welcome to YT!
I use two products for my little guy that might help you. They're both available online from one of our fellow YT members, Kathryn. Her online store website is
www.beyondspoiled.com. And trust me, she will spoil you.
For the bad breath, try using Petzlife Oral Care gel or spray. I prefer the gel, Tetley doesn't like it when I spray him in the mouth. He likes the taste of the salmon oil gel.
For the constipation, perhaps he's not getting enough fibre. You should try Missing Link supplement, it's full of fibre and omega fats which should help his digestion. Just start small with just a pinch on his food and work up to about half a teaspoon. It also needs to be refrigerated.
Good luck, let me know how it goes.