Friend, when a dog is having trouble getting up from the floor or going up stairs it is often a sign of a neuromuscular problem. It will be difficult for me to determine the exact underlying cause without a hands-on examination and some testing. But, common causes are arthritis of the hips, knee problems like a luxating patella, a pinched nerve along the back as a result of a slipped disc, etc. to name a few causes. I am not 100% certain if the vomiting and loose stool she had a few days ago is related to the weakness in her back legs. But, sometimes when a dog is systemically ill as a result of things like kidney or liver disorders, infections, tumors, etc. they can also become weak and appear to have a neuromuscular disorder. Unfortunately, on history only it will not be possible to determine the exact underlying cause, I am sorry. She is going to need a hands-on examination by your family veterinarian, blood work and possibly x-rays as an initial screening test to determine the exact underlying cause. Treatment will be based on exam and test results. Do Not give over the counter pain medication, most are toxic to dogs and will interfere with certain medications your vet may need to use. In addition, if she has something going on systemically over the counter pain tmedication can make things worst.
I realize that this answer may not be entirely to your liking, and I regret being the bearer of information that you really don’t want to hear. But it would be unfair to you and unprofessional of me were I to provide you with anything less than truthful and honest information. I hope you understand. For now, I would keep her on a bland diet of rice with boiled boneless chicken or ground beef until she is seen by your vet tomorrow.
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