2002 GT wiper issues

I have a 2002 GT with about 72000 miles and at the beginning of the winter I was having some issues with my wipers, the drivers wiper would go off the side of the car, (has happened on every GT I have had) so my boyfriend tightened the bolts and all was good, then it started again and worse and the wipers would go halfway and stop, now the may go up about 3 inches and then the SLAM down. Its annoying, I can't drive if there is any rain or snow. I am trying to figure out where to start, Any suggestions would be much appreciated!!