First, I am glad to hear that her gums are normal, but if her belly is tense and she may have eaten something harmful, then we need to be very careful here. The shaking is just a non-specific sign that she feels unwell but her getting up and being restless fit with the belly pain.
In regards ***** ***** our main concerns besides something she ate would be a possible bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, or possibly secondary to a systemic (organ, metabolic issues, etc).
With this all in mind, since she has just vomited, we will need to rest her stomach for a few hours. Water can be offered in sips but food withheld. If she can settle, we can then try her with an OTC antacid like Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac), or Milk of Magnesia (0.5tsp every 8 hours). Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, do check with her vet before use if she has any known health issues or is on any medications you didn’t mention. As well, if you try this and find her nausea too severe to keep it down, then that is usually a red flag that we need her vet to bypass her mouth with injectable anti-vomiting medication.
Once that has had time to absorb and she is steadier on her stomach, you can consider starting her on a light/easily digestible diet. Start with a small volume (a spoonful). Examples you can use are cooked white rice with boiled chicken, boiled white fish, cottage cheese, scrambled eggs, or meat baby food (as long as its garlic/onion free). When you offer that spoonful, give her 30 minutes to settle. If she keeps the food down, you can give a bit more and so on. As her stomach stabilizes, you can offer more. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset and will reduce her diarrhea. Once she is more stable, you can even add fiber (ie weetabix) to bulk up the stools quicker. As long as improvement is being seen, I usually advise that the diet be continued until her signs are settled, and that they are then slowly weaned back to their normal diet.
Finally, since you didn't see blood in those stools, you can consider trying a pet safe anti-diarrheal. As I am sure you appreciate, these would not be a cure if the cause were infectious; but it can still be of benefit. It will reduce diarrhea load, allow the body to absorb more water/nutrients, and soothe the upset gut. In regards ***** ***** options for your wee one, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p). This is available OTC at most pharmacies. Otherwise, Propectalin, Canikur, Fast Balance, and Protexin Pro-Fiber (which is available OTC at vets, pet stores, and even Amazon) would be another option. All will slow diarrhea and those last ones have the added bonus of providing support to the delicate good GI bacteria. So, these can be used as a short-term means of soothing this upset GI.
Overall, a wide range of agents could trigger the GI upset we are seeing. The shivering is a minor sign but the tensing does raises concerns here. Therefore, in her case, we’d want to start supportive care to settle her stomach. If she cannot keep that or water down, appears dehydrated already, or doesn’t respond to the above or is very sore; then we'd want to get her vet involved. They can assess her hydration, rule out fever, make sure there is nothing in her stomach that shouldn't be there or any sinister viruses present. Depending on their findings, her vet can treat her with injectable anti-vomiting medication, gut safe pain relief if needed, +/- antibiotics to settle her stomach, and get her back feeling like herself.
Finally, just to note in case you were keen to have your wee one seen today, some vet practices in our country have office hours today. As well, I wanted to mention that most veterinary practices here do have contingency plans for emergency care for their patients even when they are not open. Therefore, it is worth ringing the practice. If they are open, they will see you. If they aren't, then they will likely have a message to direct you on how to contact their out of hours service. And if you don't have a vet you can find a local one via the RCVS Register (http://findavet.rcvs.org.uk/find-a-vet/) or Vets Now (http://www.vets-now.com/find-an-emergency-vet/ ) who are open all nights/weekends. In any case, there are options to see a vet locally today too.
Please take care,
If you have any other questions, please ask me – I’ll be happy to respond. **Afterwards, I would be grateful if you would rate my service by clicking on the "Rate my Expert' button at the top of the page as this is the only way I am credited for helping you. Thank you for your feedback!: )