It's not the guage of the string, it's a problem with the instrument.

Where does the string break? My guess is it's at the point where it passes through the hole in the tuner. If so, you may need to round off the edge of the hole... I once had a similar problem with my old Eko Ranger 12...

It's just possible that it's the way you wrap the string round the pin. Thin strings need AT LEAST four turns around the pin to stop them slipping, and it's bad practice to pass the string end through the pin twice, as thisd often results in breakages. It's also vital to make the windings very neat - not crossing over, which can cause a weak point.

On the other hand, if it's breaking at the bridge, look for something that may need attention there.

String breakages on my instruments (6 & 12 guitar, mandolin, banjo) are very rare. I only have to change strings because they are past their best, and they don't drop out of tune after I've fitted them, because I pay great attention to how they 'lie'.

I frequently change my strings when I arrive at a gig, and never have tuning problems. No, I'm not bragging, just offering my technique as advice.