6-7 week kitten - bloated

I picked up my kitten about four weeks ago; the owner told me he was 6 weeks old, was litter trained and had been worm and flea treated. We knew this was a very young age to leave the mother and asked if we could come back in a week or two to get him but the woman said that someone else would take him if I didn’t that day, so I thought either way he will not be with him mum and I know that I will give him a good home! She gave me a sachet of what she had been feeding him which was whiskers adult food, but at 6 weeks I thought surely that’s too heavy for him and went out and bought him some whiskers kitten food. Two weeks after having him, we noticed his (sounds gross) anus was sticking out and had a bit of a bloated tummy. We took him straight to the vet (assuming he was roughly 8 weeks at this point) to be told he was actually only five weeks old and the woman had lied!!! They checked him over and said he seemed healthy, felt around his belly and said it was nothing to be worried about. A few days later his bum looked much better and his tummy wasn’t as bloated either. We have been giving him this sloppy food for kittens under the age of 12 months that the vet recommended and they also said to try giving him some dry food as well. He eats often, drinks occasionally (sometimes we give him water through a syringe when he seems dehydrated after pinching the scruff to see if it springs back) he seems happy, he is very playful, loves to bite and overall he is absolutely adorable!!

Anyway, a majority of the time his stomach is bloated, and last week he was sick a tiny bit. I rang the vet and they said it is probably the change of the food. I am still very worried (I am paranoid and negative about everything) is it the change of food or is there something wrong with him? Is it normal for kittens to bloat when they eat? And how much/when should he be eating? (Bearing in mind I am at work 9 hours a day).

Has he been de-wormed? That's probably what it is. Ask the vet for some good de-wormer.

But it is normal for a young kitten to have a fat tummy after eating. They're so small that even a little bit in their tummy will make it look fat.