Cycle day 47 late 13 days!!

I don't know what my deal is. I am 13 days late and on cycle day 47? I took a pregnancy test a couple days ago and it was negative. Please help, do you think I'm pregnant? Have you ever had a cycle this long? I worry because I found out later on with all 3 of my pregnancys. I was 7 months with my last! I don't want that big of a surprise this time!! I need a lot more time to prepare! PLEASE PLEASE GIVE ME ADVICE!