Can I ask what breed this is?
How old is the dog?
Are eating drinking and elimination habits the same?
Thank you for that information. The Cocker spaniel breed is prone to two things that may be causing the problem. The first, which I think may be the problem from the symptoms you describe, is Intervertebral Disc disease which is when a disc gets a hard build up of substance that pushes against the spine causing pain and difficulty walking. Symptoms are back pain, reluctance to play, yelping when handled,walking drunk inability to walk or paralysis. Your vet can determine how bad it is and what treatment is necessary. If it is mild, generally an anti inflammatory drug is given along with lots of rest. The worst case scenario is surgery.
You can read more about this here.
The second thing Cockers are prone to is Hip dysplasia which is when the femur does not fit into the hip joint. This can result in lameness. You may notice an abnormal gait. or reduced function in the hind legs. Reluctance to run and jump, hardship in getting up and down are symptoms. Pain medication may be given or surgery may be another option. You can read more on this here.
Okay, I understand your confusion. My apologies, I believed you to say she yelped when touched near the hind end, not on the belly.
This would mean that there is a possible problem with stones in the urinary tract, kidneys or bladder. This can be genetic, related to diet, a metabolic disorder, or a bacterial infection. Have you noticed any difference in urination? Any accidents around the house? Any blood in the urine? These would be some signs of a bladder stone problem. (This is also a problem found in Cocker Spaniels). Some dogs do not display all the symptoms of bladder stones however back and abdominal pain are also signs.
I am directing you to a site on urolithiasis (bladder stones) to further assist you, and again I am sorry for the original mix up, I know how scary it can be when our pets are sick.