Pregnant or stress?

So for the last 8 months I have been very regular, by the 4th day of every month I start my period. Last month I was 2 days late, spotted for half a day and nothing after that. This month I am 6 days late, no spotting and no indication that I will start soon. I have been incredibly moody and emotional and have been under some stress. Have also had increased acne which only ever had when I was pregnant with my daughter. I took a pregnancy test last month and said it was negative but now am starting to wonder if I am. Can anyone please give me any advice??