What Causes Lower Back Pain And Abdominal Cramps After Menstruation?

Hi, Ive had a painful lower back since saturday and its now monday. also I have had tummy pains like period cramps but i jus finished my period about a week ago now. I am on the contraceptive pill but i have missed quite a few but still been having intimate sessions with my boyfriend unprotected. also my breats are very painfull all the time, espeically when playing netball or riding my horse. my upper legs also feel like they are cramping up alot too. I have also been feeling nausiated alot and the smell of raw meat or mince meat sets me off.

please let me know what you think might be going on with me as i have not enjoyed this at all and would like to get rid of it.