I have an Aveo 1.2 2009 model

I have had a problem with break lights for some time , fuses kept blowing , finally got car into for check and was told brake switch was done, new switch fitted and all was fine for around 3 weeks. Now lights out again - fuse is fried and when you put new fuse in lights work again but for how long!! Any ideas on possible causes of the fuse to blow?