Lola is very sensitive when it comes to food, she has lots of tummy issues if i feed her human food, or if she eats grass or whatever is not her kibble. When i first got her I remember the first time she had tummy issues, she would't stop shaking, and the shakes came from her belly, I took her to the vet and she told me it could be gas from her food, the vet gave me a natural medicine for digestion problems.
Even when I don't ever give her any human food and i am always telling ppl not to feed her cus she is very sensitive, sometimes she gets " the shakes" , i give her her medicine n after 5 min she is completly fine.
wherever i go, i take the medicine with me cuz i know she can get an upset belly anytime and i am sure is very painfull, u can feel her hard stomach and the look in her face is heartbreaking.
maybe u can try to find the medicine, i buy it on line, the name is Digyton from Himalaya, here is a link with some info.
Digyton - Stimulates the secretion of proteolytic, amylolytic and lipolytic enzymes, Acts as a carminative, Tones the digestive glands and organs and Corrects gastrointestinal disorders - Himalaya Herbal Healthcare
Good luck!