BBT chart help I'm late


So I am 2 days late and my BBT is going up. I know that after day 16 of high temps that can indicate pregnancy, I'm on day 15 of high temps. I took Prego tests and I saw a vvvvvvvvfl on them but I had to really look. I normally have 26-28 day cycles the longest is 28 days and now I'm on day 30. I had brown spotting only sometimes when I wiped yesterday and the day before. Any thoughts on this and the chart? The only thing is why wouldn't my test lined be dark on 15 dpo? Thanks ladies!