Hello Keren, I'm Dr. Deb.
I recently came online and see that your question about Judd hasn't been answered. I'm so sorry that you've had to wait for a response,but if you still need assistance, I'd like to help if I can.
In a situation like this where there's an acute onset of pain which may be difficult to localize, then there are several possible explanations. If he had pulled a muscle or was experiencing a sprain, I'd expect him to be lame on at least one leg or to show pain in only one location on his body although I can understand why you might think this could be his problem.
If this were my case, I'd want to consider the following as possible reasons for his behavior:
1. Tick disease.
Symptoms can include fever (normal is between 100 and 102.5), lethargy, stiff, achy body (like the worst flu you've ever had), and sometimes lameness or swollen joints. But the absence of these last two signs doesn't necessarily rule out this disease.
We do have tests for many of these diseases, but we are testing for antibodies, not the organism itself, in most cases. If antibodies are not being produced (for whatever reason) then the tests could be negative and yet this is still the underlying problem.
I've also come to believe that there are tick diseases that we haven't even been able to identify yet and thus would not have tests for all of them. I say this because I live in an area of the country where ticks are endemic. I see dogs present just as you describe I run every tick test that is available (if the owners agree) and yet, many times, they are negative. However, once tetracycline-based drugs are initiated, my patient improves.
2. Problem with the spine such as a disc compressing the spinal cord. These dogs can be quite painful and are often walking with their backs hunched. They may or may not be lame or favoring one or more legs. If the neck is the problem, then they often don't want to turn their heads or hold them down.
A physical and/or x-rays may be suggestive but often an MRI is needed to definitively diagnose this condition.
3. Another possible explanation would be a condition called Discospondylitis (link) which is an infection along the vertebrae. Usually this problem is very painful especially when you press on the back.
Judd might benefit from a non-steroidal anti-inflammatory drug such as Aspirin at a dose of 10 mg/lb twice a day, given with food to avoid stomach upset.
I'm often hesitant to suggest it's use since it might interfere with what your vet would want to prescribe but several doses should be find and may bring much needed relief from Judd's pain.
I hope this helps; again, my apologies for the delayed response.