What Causes Delay In Periods And Breast Soreness Despite Having Negative UPT?

I have taken 2 pregnancy tests in the last 2 days on yesterday around 10 am and one this morning right away around 5am both are negative bit I'm on day 47 of having no period. I normally have irregular periods but even this is a long time for me to go with no period. I don't have many signs of being pregnant just sore breasts and a bit of cramping that is it that's also normal for me before my period. What could this mean.