

4 week old kitten hasn't pooped in a week, yet vet says he doesn't have any poop in him
Reposted because I accidentally doxxed myself.
I'm 25 years old and I live in Turkey. My kitten hadn't pooped in four days so I took him to my veterinarian three days ago. They inspected his belly, cleared his anus with a lubricated thermometer and took a few x-rays of him. She said he only has a tiny amount of poop but lots of gas. It has been 7 days in total since he last pooped.
I am going to take him there again two days later but I wanted to get a second opinion because kittens can deteriorate very quickly.
- His mom was a stray cat, she apparently was killed by dogs. He has two other siblings who are fostered by someone else and they're pooping alright.
- He's been with me for 25 days and we think he is around 27 days old.
- He did have fleas at the beginning but I was able to take care of that and all the fleas are dead, no eggs remaining.
- He has been dewormed with Pyrantel pamoate.
- No history of diarrhea, vomiting, nausea, lethargy or lack of appetite.
- He did have trouble pooping since the day I got him. I had to gently squeeze his belly and stimulate his anus for 15 to 30 minutes to get him to poop before. But his poop was never hard or dark colored. No parasites, eggs or blood present either.
I had taken him to an animal hospital two weeks earlier and the doctor there suggested adding extra water to his formula, giving him a drop of olive oil every feeding and also prescribed two drops of Simethicone daily. I have since stopped doing all these things in accordance to my recent vet visit.
His appetite is great, he pees adequately and his pee is light yellow, he loves to run around, play and climb, he likes to have his belly rubbed and he loves to shove his face into my beard. I really don't want to lose him and I'm just stumped. How can a kitten keep gaining weight but not produce any poop for a week??
EDIT: A few hours later my mom came to help me and she made him poop. I suppose I was too soft on him, she squeezed his belly and didn't let him go for five minutes. He really scratched her arm trying to escape but she didn't let go and kept massaging him. He pooped one solid poop and was relieved. Poop images in comments if you're curious.