Kitten with diarrhea not responding to meds

I posted awhile ago with concerns that my five month old kitten might have giardia. After taking him to the vet and having a fecal exam, they ruled that out and thought he had a bacterial infection. He's now had two rounds of Metronidazole. The first time with a round of Panacur (they treated him for giardia just in case). This latest round, after the fecal exam, with Amoxicillin. They thought it was an infection because he also had a slight temperature which I've been monitoring at home. That has gone down. However, even after seven days of medication, he still does have runny stools. It's like chocolate syrup. It's that color and just a little thicker consistency. I'm not seeing mucus like I was but, he has also now thrown up a few times. His appetite is lacking but he does still eat some. I just don't think he's eating what he should. His attitude has also gone from wild and crazy, playful kitten to wanting to sleep all day long. I'm scared. The vet told us to bring him back if he didn't improve after medications so that they could run blood tests. I'm just wondering if anyone has had experience with anything similar in such a young kitty. He's just five months old. We got him because we just lost our first and oldest cat and I can't handle losing a kitten. Please help!

What kind of food are you feeding? It's possible it could be from food, but I don't know if the meds would clear that up. My one cat had runny poop when I was feeding Nutro Natral Choice. When I switched to Weruva it stopped.

Food DOES make a difference!

I am feeding Merrick dry kitten food. He was getting a little bit of Solid Gold Tuna in gravy but I've stopped giving that. He hasn't had any for days now.

glad you got rid of the tuna food, that's really not the best thing to be feeding him.

http://www.thecatsite.com/t/2815/feeding-cats-tuna

Since he's so young, I would put him on Wellness Core Kitten Formula. A lot of rescue places use this & I started my cats off with it too, it's a pretty good kitten food. Using the Merrick plus the Wellness would be good for him. Remember to keep him on kitten food until he's about a year old.

Another thing I would get is a probiotic, that will help immensely with the gut

Probiotics. I can't stress enough how important they are, especially for a kitten recovering from both an infection and medication. Here's a great article about probiotics and which (human) ones you should use. I use Nexabiotics, for both my adult cats and when my (now over a year) kittens were tiny. It's very safe and very effective in healing kitten diarrhea, just mix 1/2 capsule in wet food AM and PM. 

http://www.rawfeedingforibdcats.org/probiotics-for-cats---why-and-which-ones.html