Sorry to hear about the struggle with ants.  Ants are bugs and like most vermin, they hang around if they have food/and or water.  Bathrooms provide moisture and, I think, they are sometimes attracted to the sugar in toothpaste, of which, there is likely residue everywhere, even if you clean your bathroom regularly--it just carries  from the micro-water droplets from when you brush your teeth.

Ants are also special because if your home is built over a colony, you will get them if it rains or the ground gets wet.  I know because I've lived this.   Raid isn't your answer.  The best my wife and I found was to have pest control come out.  They will ant bait around your house and put this gel substance in the nooks and crannies of wherever you seem to see the source of your ants in your home.

Ants may need food and water to thrive like all other bugs in a home, but they are... special because they are the definition of explorers in the bug kingdom.  They go where the smell "food", even if it's not there.  Fortunately, if they aren't anything but piss-ants (sorry, I don't know what else they are called) then they are really just a nuisance and not a real problem.  And by "problem", I mean they don't bite and don't really ruin or damage your home.  They are super-annoying, though and when we moved one of the greatest highlights was getting away from the dang ant colony our home was built on.

(FYI, we bought the home brand new and lived in it for about 5 years.  We kept the ants away most of the time by frequently calling pest control, but if we got a heavy rain, there was no stopping it.  The ants would move to get away from the rising water. You might be in the same situation.)