not sure of symptoms..

my periods are usually irregular (I think anyway). had intercourse on what glow said was my fertile window, a couple of weeks ago. I keep getting light cramping as if I'm coming on, today there's a tight feeling and emotions are all over the place. have been having diahrroea today too with a bit of nausea, quite tired and sore breasts. not sure if any of this is just me being run down, whether I'm coming on my period or whether I may be pregnant? any one else experiencing this?