My dog seems dizzy and have walking problems.

Vet now!  Those are not good symptoms -- could be a raging ear infection, but those can spread down the eustacian tubes and be really hard to deal with ... and yes, they can go to the brain and cause encephalytis (which is fatal).  any time you see a lot of head-shaking it's time for the vet.  Ear infections can be extremely serious.

I'd get him to the vet today.  A dog this young with that sudden a change needs to be vetted.
 
While you are there, have the vet do a fecal.  Worms or parasites could be responsible for the weight issues.  While leaner is better on large breeds, too lean is not great.  I have a shepherd who I have been consistently unable to keep weight ont his winter and it's nothing more than him needing extra calories because of the cold.  He's been vetted, no problems, but he looks like a bag of bones.  The other two boys are a bit thin, but poor Thunder looks anorexic.  He gets more than 2200 kcals for breakfast ALONE!  Sometimes with active dogs with fast metobolisms the cold weather is just enough to require way more calories.
 
But truely, that head shaking and the dizziness could be anything from something IN his ear, to an infection, to vestibul disease to a tumor.  Get him to the vet ASAP.

Callie and Glenda are experienced owners - please take their advice.  It seems your dogs symptoms are worsening.  He should be seen by the vet asap.

What food do you feed him???
As Glenda said, he may need more calories.

Vet is in order here for sure.
 
Whip worms will cause no weight gain as Glenda points out.

Another thing that can cause your dog to stumble like he is is a tick. Search his body to make sure he does not have a tick embedded into his skin. This can cause what you describe and can totally disable the dog to not walk at all.
Head shaking can be anything from ear mites to ear infections. This needs to be addressed by a vet and very soon.
Please let us know whet the out come was from the vets office.
Sending your fur child healing vibes.

I hope you take your dog to get him checked. I hope he has an infection or something that can be cleared up quickly.  
Please keep us posted.

I don't know what it could be but take him to the vet to get it checked.  And, then please update us and I wanna see a picture!

Thank you for the information. He has ear mites, vet said he should be ok and he seems to be getting better,is back laying and walking normal.
 
They took some blood samples and are gonna call me back. Also, I checked all of his fur for ticks, thankfully did not find any.
 
I was informed he is at a healthy weight, but could stand to gain a few pounds. His weight was 72.3 pounds.
 
The food I have been feeding him for about the last 3 months is Pedigree canned food with dry food. I normally feed him twice a day, in the morning 2 cans of food, with 2 parts dry, each can is 13.2 oz and then do the same for dinner around 4pm. Some times he finishes it all, sometimes he snubbs the dryfood and sucks out all the wet food. I do not like to feed him strickly canned food because he ends up having diarrhea.
 
The vet offered me some vet brand food, but it was 35 dollars for a 10 pound bag. I am a full time student and just the ear bill alone hurt.
 
Again, thank you for the information and if anyone has any good feeding tips I would be very thankful to hear them.

I truely understand finances being tight.  However, Pedigree is primarily corn and grains and lots of grain fragments.  Little meat if any, and I don't know without going and looking at a label online.  Since you are paying the price for canned and dry, you wouldn't be spending a whole lot more if you went with something of a higher quality like Wellness, Eagle Pak, Chicken Soup for the Dog Lovers Soul......I'm thinking all three of those are on the lower end of the price range.  Innova is what I feed my gsds, but it will put you into sticker shock.  However, I feed Innova for breakfast to SIX german shepherds and a bag lasts me a full week.  So it should last you about 3-4 weeks.  it's around $40 for a 33 lb bag, but I'm guessing that you spend very close to that on the amount of Pedigree that he's eating.

You'll feed less of a high quality food than you will Pedigree, so some of the cost will be made up.  Also, you should consider that a dog on an excellent diet should have fewer vet visits over his lifespan than one who eats the canine equivalent of junk food.  If you want to learn more about canine nutrition and get some suggestions on foods that are a little higher in quality but which you might be able to afford until you get out of school, visit The Dog Food Project at [linkhttp://www.mordanna.com]www.mordanna.com[/link].
Glad you got to the vet, though, and that your dog is feeling better.