@WhatGatsby No one here can tell you what you need. We aren’t the admissions committee. We didn’t see your original file and we don’t know your circumstances. If you want to attend one of the universities that originally admitted you, contact them and say so. I also strongly advise that you supplement your application with a letter to the Admissions Director, stating why you want to attend, why you originally decided to go elsewhere, and anything that has affected your performance at Amherst. If you have credentials that can strengthen your case–higher SAT scores for example–by all means submit them.
Again, rather than asking outsiders for advice, contact the universities concerned. Good luck!