Hi Shelly,
I am not a vet so it would be best if you only use these comments to ask your vet some questions and get the correct answers from him/her. I wanted to clarify, was the hematoma at the site of the cervical surgery from 3 years ago, or the lumbar surgery she just had?
I am pretty sure it is not your technique, so the part about "are you incompetent" does not sound likely--you've managed fine so far.
If you think it is a matter of willpower on her part...this would not be my first guess but it is possible. Perhaps you could try taking her out to her favorite potty spot outside, if she has one, and see if she is "willing" to either go on her own or to let you express her there.
A rigid abdomen could be due to pain. If she is not on pain control you may need it for a while.
She could be uncomfortably constipated. This can happen from stress, medication, immobility, etc. It can make the abdomen firm and make it very hard for you to feel the bladder. A side effect of all this is that the discomfort of trying to express a really constipated dog may make the dog tense up. There are various ways to deal with constipation, I recommend lactulose syrup from the vet. Please do not try any human laxative without asking your vet first, some of them are poisonous for dogs.
Here is a long explanation for something that may not apply to your situation, but I'll offer it anyway. There are 2 kinds of incontinence. In one, the bladder is easy to express and the dog may even dribble. In the other, the dog has a very tight sphincter and does not dribble and can be difficult to express, to the point that it may require a lot of pressure and some people turn to medication to relax the sphincter. The easy-to-express bladder usually goes with a lower motor neuron problem, which is a problem in the lower back. A hard-to-express bladder (like my dog has) goes with an upper motor neuron problem (injury to the mid- or upper back).
If I understood correctly, your dog had a lower back (lumbar) problem and had surgery on the lower back recently and was easy to express. That makes sense: lumbar problem, easy to express.
One other possibility is some sort of blockage. Again this would not be at the top of my list, but we did have a dog just this week with stones. You do not want to put too much pressure on a bladder that is truly blocked. I think you might need to have the vet check her just to be safe.
Whatever may be causing it, she does need to have her bladder emptied. You may need to take her to the vet, or even the nighttime emergency vet, to see if they can express her. I hope you'll let us know how it goes. I'll be waiting to hear if you got her sorted out. Bless her heart, and you because you've been through the wringer with all this. This is more than most people have to go through, and the usual amount of stress without complications is a great plenty! If she has deep pain, can wag her tail, and is moving her foot a little, that is very encouraging.
