Well, I've had three chihuahuas and one yorkie prior to Kacee. None of the previous one's had any trouble at all. Along comes Kacee and breaks the mould. She had an upset stomach and a little diahrrea with it. She had quite a time putting it mildly. She was so sick a couple of days she barely got up and around. I knew it was her teeth. Mother's just know these things!
Thankfully her teeth are almost all through her gums now. I really felt sorry for her, because I have never seen one feel so bad as she did. My vet said they are just like children. Some have little or no trouble, while others have a terrible time with it. Of course, you should check with your vet just in case it is something else.