Thanks so much for the additional information.
Gum color is normal which is good.
1. I do understand about taking her temperature. It's too bad that it's stressing her out so much since it would be good to know if it's elevated since a fever could explain her sudden symptoms. If you manage to take it (if you have someone to help you), normal is between 100 and 102.5 F. If it is elevated, then this explains the lethargy but we don't have a source of the fever. Possible explanations for a fever would include:
a. Tick diseases can cause fevers and achy muscles. They can occur quite suddenly with no warning. These could be ticks that fed months ago (lyme disease) or even one week ago (Rocky Mountain Spotted Fever). 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.
Doxycycline is the drug used to treat most tick diseases.
b. Leptospirosis can mimic tick diseases but can affect the kidneys and/or liver. This disease is primarily transmitted in the urine of wild animals. Dogs can ingest the organism when they drink stagnant water in which a critter has urinated. Blood work would be needed to determine to evaluate these organs. Some dogs can become very ill with this disease; some can even die from it (obviously the worse case situation). Treatment is amoxicillin and/or doxycycline. Humans can contract this disease if it is being shed in their dog’s urine.
c. Some sort of bacterial or viral infection can cause fevers and/or lethargy.
d, Autoimmune diseases can also cause the temperature to be elevated.
2. Dogs with spinal issues (compression of the cord by a disc, for example) can be painful and behave as you describe. It's possible that her run-in with the door caused more damage than was apparent at the time.
A good physical exam might reveal abnormalities or additional testing might be required.
In general, dogs with injuires of the spinal cord are better served if seen sooner rather than later.
3. I've seen a few dogs just have "off days" for some reason which usually lasts about 24 hours but they aren't usually painful, so this is less likely.
I'm hesitant to advise any over the counter medications until a better idea of the problem is known. But, if she's not vomiting and you can't have her seen today, then you could give her Aspirin at a dose of 10 mg/lb twice a day, which would be 1/2 of a 325 mg (full strength) tablet at one time.
I always suggest that this drug should be given with food to avoid stomach upset. The anti-pain as well as anti-inflammatory properties of this medication can be useful ini situation such as this.
I hope this helps and that she's feeling better in a very short period of time. Deb