Kitten on antibiotics- stool help

Hello, my 12(ish) week old kitten Ghost has been on antibiotics for a week because he had a tummy bug. I'm not sure what antibiotic he was on OR what the tummy bug was. He's a rescue, so it basically got lost in translation between the foster, adoption coordinator and me. 

I got him last Saturday and he was on Purina Kitten (pink bag) but I only got a little bit of that with him and really wanted to switch to something at least a little bit better. I bought him new food (Go! Daily Defence dry and some Go! wet food- I went with a brand I would feel comfortable feeding my dog) and I leave the dry out for him and give him a 1/4 large can in the evening. I won't free feed forever, but that's what is working for him right now. We came from the vet yesterday, and he doesn't seem too concerned about loose stool at this point because the antibiotics can cause it and it could be due to the switch in diet. This morning he has a really mucousy stool and it was overly stinky. 

This is my first cat of my own, I'm honestly not sure what their poop is supposed to look like. He's 3.4lbs right now and gaining weight normally. I'm hoping to switch to raw in a few weeks after I settle in my new house, but for now could someone please tell me if I should be concerned? How long should it take for the diarrhea/loose stool to go solid after antibiotics? 

Here's my little guy:

He may need a probiotic to get back to normal after the antibiotic and help him through the diet change. Benebac is a good one you can buy at pet stores, or your vet might be able to give you one, or recommend a brand. You can also try mixing a little bit (a teaspoon or less) of plain canned pumpkin with his food once a day. The fiber helps to normalize a cat's stool. It should look like solid "tootsie rolls"; mucousy & super stinky is definitely not normal.