No af but bfn?

Rebecca
I was due my period last Thursday the 7th, it is now 11th and still no af. I did 2 tests one Thursday and one Friday but both negative. My boobs have been achy and slightly sore so I thought this was it, but no bfn :( my cycles are really irregular as well so maybe I'm just having a longer cycle I'm not sure. Any advice? Xxx