Topic: What causes delays in processing time?

Hello my name is Mira. I was wondering what could cause a delay in the processing time of i485 . We took our time after arriving in the US to file the form(a year and a half to be honest) and my PD is July 9,2013. I received a work authorization card in December 2016 but haven't received any other further notice of actions since than and I am getting quite worried! I filled an e-request for forms taking more time than the ordinary last month but still no answer. Does anybody know what is the best way to contact the uscis or the best way to check on your case status? Because frankly all those tools and calculators online doesn't give you anything more than you already know