Potty problems with the boy I babysit

Okay this may be blunt but it is what it is. I watch this boy every Saturday. He is 2 months shy of age 3. He’s not potty trained whatsoever. He is also extremely shy. He lovesssss coming over to my house because that’s all he asks his mom to do when they’re home. But while he’s here he literally does not say more than 3 words to me. At all. Which is fine we play and cuddle on the couch. Which leads me to my problem. He willl not tell me when he’s used the bathroom in his pull up, but I know at his home he will tell his mom he needs to be changed. I basically have to feel and guess when to change him it else he leaks through his pull up and onto my couch. Then I have to wash the entire thing. I’m getting tired of doing that EVERY week. I need suggestions on what to do. Right now I change him every 2 hours and he still will leak

ETA: his parents aren’t actively potty training. Just change his pull ups when necessary