Road Bike Issue

Hey guys,

I'm looking for some serious advice here. I've been riding my bike into work lately (about 21 km each way), and for the last 3 days, at some point in the morning, my front tire goes completely flat. I'll do a quick tube change, ride home, get the PSI up to 115-120, ride to work the next day, then have the same problem all over again.

I check my tire for sharps and debris at each change, am careful on my rides to stay on the nice part of the road (no bumps/potholes) yet have this problem. The only thing I can think of is it is sitting on the south side of the building in the sun, and over the day it gets too hot. Anyway - I'm running out of money for tubes and patch kits..

Any thoughts on what causes this/what I can do to stop it from happening?

Thanks