In the last 2 days my alternator belt has came off or been shredded twice cause

Any noise , prior to belt 'shredding'?

Check the 2 idler pulley bearings and the tensioner pulley as well. If any of these have bad bearings you will have belt misalignment which will destroy your belt in no time You also may want to check and see if the harmonic balancer is coming apart. I had all of the above issues with my Aztek. All parts are available at your local auto parts place.