My Last Period Was December 31st 2015, I Didn't Get

my last period was December 31st 2015, i didn't get a period in January which was due the 29th i took a pregnant test the first day i didn't get it and it came back negative and then a week later i took another one still negative well now im two months late and not sure whats going... could there be possibility that i could be pregnant? or what might be there reason behind all this?