Smells like coolant leaking but cannot find a source

I believe my car has a coolant leak as there is a
sweet maple syrup like smell and I’ve had to add
more coolant recently. The leak appears to be slow,
as I haven’t seen dramatic changes in levels. I don’t
know a lot about cars, so I took my car into two
different shops where they were both unable to
visibly see any leaks. I haven’t noticed any leakage
on the groud after I’ve been parked. It smells sweet
inside the car as well and in the winter my windows
have occasionally frosted over internally (I’ve heard
this can be related but like I said I know little about
cars). Any recommendations on what to do? I don’t
want to cause any further damage that could be
more costly. Is it still okay to drive regularly?