Period ended but still getting symptoms

So I've finished my period 3 days ago, it was shorter than normal (3/4 days and not heavy bleeding. Normally 7 days without fail and clots and very heavy.) I had BFN a day before so thought okay that was it, period done and dusted and move on but I'm still getting symptoms. I am still getting sore breasts, headaches everyday, cramps, backaches, feeling sick all times of day and mood swings are terrible. Have anyone had this after there period? I have done tests and I'm sure they're BFN. Any advice would be brilliant!