Confused and stressed

I have only been using glow for a couple months but I had been tracking my period since August. When I started glow I entered in all my past periods and all my cycles are 30-33 day cylces. This month I have racked up 48 days so far! Since today was my 15th day of being late I took a test and got a negative.... I'm going to try again in a couples days but I do have to say I was quite disappointed. Anyone else have this happen?