A senator is a congressperson. You likely meant senator vs representative. As to which one is more helpful depends on the contacts/liaisons that congressperson has with USCIS.while we are on this topic, which politician is more helpful (powerful) if running into problem with federal agency like the USCIS, the congressman or the Senator (one of my state's US senator has pretty high seniority in the Senate)?
^^^I thought you're from New York. I can't imagine Chuck Schumer or Kirsten Gillibrand helping people out with immigration cases. I think a Representative can help you out better as they have a smaller constituency as opposed to the whole state.
USCIS and even Canadian Immigration (and perhaps any immigration process) would usually say that making inquiries into one's case may delay it further. There really is nothing one can do but play the waiting game with them otherwise go crazy. I applied for my green card in early 2005 and got it issued in September 2007. Talk about delay. I really did not bother checking on it, I was just glad I was able to work, school, and be productive, etc. Finally able to file the N400 now simply makes my case no different than a 5yr application because that is really how long I have waited if you total all the waiting period from filing my green card till now. Try the suggestions you get, they may or may not help, you may simply still have to wait.
if you care to look at green card section of forum for employment based categories, I am sure you will find lot of people waiting for GC anywhere from 4-6 years (if not more). This waiting does not count towards citizenship. Senate/representative offices do have liasions to help/assist constituents with immigration related issues. In most cases than not, congress person liasion have been proved to be of help. I am sure when one is waiting for green card approval (be it may 6 years or more), they need to be more productive to keep job and keep green card hope alive. Please do some research to be more infomred. No two cases are same.
as to OP, since it is 3 months (about 90 days), start with congressperson (Senator or representative). This being election year, in my opinion congress person will be willing to assist as much as possible and may be able to provide you with reason for delay.