My Cat Is Weak, Won't Eat And Sleeps All The Time, Why?

Your cat needs to be examined by a veterinarian.  Not eating is a very vague sign of illness that is noted with most diseases.  Anything that causes discomfort or lethargy can cause anorexia.  Diagnostics needed may be blood work and x-rays.  Treatment will be aimed at the disease process and include supportive care.  With cats it is very concerning when they stop eating because they can develop a secondary condition called hepatic lipidosis or "fatty liver disease" secondary to not eating.

My cat is acting really different and I'm scared, she can't jump on the bed or chairs. And is just laying around the house. She eats n drinks a lil but isn't herself. Why

This cat needs to be examined by a veterinarian immediately.  If your cat is weak it probably hasn't been eating for awhile--cats can develop a secondary disease called hepatic lipidosis (fatty liver disease) from not eating.  Many things like liver disease, kidney disease, diabetes, infection, and neoplasia are all possible causes.  Your cat needs supportive care as well as diagnostics immediately. 

Constipation is not uncommon in older cats.  It can cause lethargy, depression, inappetance, abdominal pain and vomiting.  Causes can include ingestion of foreign material (hair balls, bones ets) a narrow pelvis, a lack of exercise, a dirty litter tray, pain, tumours, medicine, and obesity.
Your cat needs to be examined by a vet to confirm this diagnosis.  A vet will do a full physical examination and possibly a rectal examination.
Treatment can be with medicine and high fibre diets but it usually involves an enema.  Minor enemas can be done while the cat is conscious but in more severe cases it may require a general anaesthetic.  Increased faecal material in the colon draws fluid out of the body and cats that have been constipated for a while can be very dehydrated.  In this case, your vet may have to put your cat on a drip to rehydrate.

This sounds very much like a problem mine and my sisters cat has.it sounds like it could be a mix of things, worms can make a cat lethargic also an allergy to fleas can have that effect,you can't stop your cat getting fleas unfortunately but a flea collar seems to work.the bad smell could be from licking himself as it spreads the food residue all over the fur(licking a lot could also be an allergy)just get a cotton pad with some cider vinegar on it and rub the fur with it..preferably after a bath,if there is an allergy it will help disinfect. As for the eyes..our cat has constantly leaking eyes and we've tried to check it out and no luck.you should take him to a pet clinic tho..the mix of things could be bad

Lethargy is condition when animals have delayed response to external stimuli. If this condition persists for more than 24 hours then visit to vet is necessary. Following can be causes of lethargy in cats.

1. Electrolyte imbalance
2. Anemia
3. Cardiovascular disorders
4. Infections
5. Hormonal disorders
6. Cancer
7. Skin and eye diseases
8. Toxic reactions
9. Side effects of medicines
10. Immune diseases

So, it will be better to take your cat to vet.

Vomiting in cats along with lethargy and loss of appetite is not good sign. This problem can be due to many reasons. Most common causes of this condition are

1. Food allergies
2. Food intolerance
   
3. Changes in food
4. Eating rapidly
5. Eating of grass or rodents
6. Exercise after eating
7. Hairballs
8. Poison toxicity
9. GI tract problems
10. Symptom of many diseases

There can be many more reasons but visiting a vet for proper diagnosis and treatment is necessary. So, take your cat to vet.

Did your cat get better?...because I think my cat has the same issue.

You should listen to AnnFalk, she is a vet and good at that. Hope this helps.

My 15 year old cat is thin but she eats and is not sick

Your cat is very sick. The problem can be with liver, kidney disease, or diabetes etc. Dry nose is just a reflection of it's surroundings and you cat can die. You can't do anything at home. You have to take the cat to the vet as early as possible.