Period late negative test..?

Hi girls, so I'm slightly frustrated I've just tested negative and yet I'm 9 days late? We are trying for a baby so if I was to be pregant then it'll be the best news ever but I can't help feeling disappointed 😔 I'm on cycle day 36 and I've never gone on this long, last month was 25 days and the month before was 31..? Any advice would be great if anyone has had the same thing...?