First, if you can't afford to take the animal to the vet- YOU SHOULDN'T HAVE GOTTEN A PET!
You obviously haven't had it vaccinated since you are afraid of Parvo- it can very well be Parvo and anytime an animal is sick for more than 24 hours, it need to be seen by a vet.
Also, it's ILLEGAL to not vaccinate your pet and ANIMAL NEGLECT to not take it to the vet when you know it's sick- especially for 4 weeks!

Many vets will set up a payment plan and they LEGALLY CANNOT deny your animal treatment. TAKE THE THING TO THE VET or it could die!

After you take it to the vet- find it a home where the person is actually responsible!

And to take it's temperature- get a regular human digital thermometer and put it in the dogs rectum about 1/2 an inch- wait for it to beep- dogs regular temperature varies between 99.5 and 101.5. Anything higher is a fever and life-threatning for a young animal.

DO SOMETHING NOW or you'll feel even worse when the dog dies because you were irresponsible!