How do I time these contractions?

Justia
Do you ladies know how to time contractions? And when to time them? 
I'm having sharp period cramps  in my lower abdomen. it seems every 8 mins. They are not unbearable though. When I moved around they stopped but when I sat down they started again. 
I don't know if this is it y'all! Or could this be false labor? 
Let me know