The English idiom "sicker than a dog" calls to mind the vivid and colorful memory that many people have of a dog vomiting, having non-productive intestinal spasms (dry heaves), or trying to pass a hard stool (the doggie jig). Dogs make no effort to conceal their distress, and so make loud noises that sound like a cross between hacking and barking while vomiting. To add to the imagery, sometimes the canine vomitus contains live parasitic worms, or pieces of offal that the dog has ingested.
Clearly a human who is "sicker than a dog" is feeling rather unwell!
It is "feel as sick as a dog." The nurse became sick as a dog after contracting the flu. Food poisoning makes people sicker than dogs. Note: This is a very trite, overused expression.
No because he/she will get more sicker and sicker and sicker
The phrase "sicker than a dog" is believed to have originated in the early 20th century, although the exact origin is unclear. It likely refers to the fact that dogs, particularly in the past, were often associated with illness due to their scavenging habits and exposure to unsanitary conditions. The expression emphasizes a state of feeling very ill, using the imagery of a dog being unwell to convey the severity of the condition. Similar phrases exist in other cultures, reflecting a common tendency to use animals as metaphors for human experiences.
Yes you can. You can get MUCH worse than it already is. 
sicker than lil Wayne cash flow
it depends on the dog, if it is a mean dog than it most likely will.
It means that if you steal and beg than you are no better behaved than a dog.
I was sick, but my brother was sicker, and our sister was the sickest of us all.
It means that not all have them equally bad. Some will be sicker, some will be healthier.
If a dog eats a lot it could mean the dog is experiencing a growth. If the dog is fully grown and is eating a lot more than normal, the dog could have worms and need medication.
no
flicker