Does taking clarithromycin irregularly result in infection causing more harm to body tissues compared to not taking clarithromycin at all?

That could happen: Germs may reproduce every 10 minutes & each cycle allows a chance for their genes to mutate & become resistant to the med. Irregular dosing allows those surviving the early doses to repopulate & potentially develop a resistance and thrive. At that point it might fail to kill the germs. If you hit the germ hard & consistently the chance of this happening is not eliminated but is far less likely.