The bike hates you?!

Seriously, ok. You checked for punctures and there were none? How is the air leaving the tube? Did you do all the normal "inflate & put in a bucket of water" stuff? What about something poking near where the thingie goes out of the hole (sorry, am blanking but you know what I mean hopefully!). Valve. That's it.

I know there are people who know far more than me but from breaking it down in a troubleshooting sort of way...the tube is losing air somehow. It's a question of how and where - ie is the rim digging in? Or is there a pinch flat? Or a batch of defective tubes? Thorn through the tire? Probably not that though if you changed the tires. Or maybe someone's messing with you when you aren't looking?

Curious.