no period

Vicky
Hey everyone, I come off the contraceptive pill nearly a month ago now and was only on it for four-five months. Annoyingly I've been having the dull cramps and acne like I normally do with period but no period yet, I've also started having slight aches in my boobs which I only get when pregnant, I haven't had a period since the beginning of September I've taken four pregnancy tests and all have been negative, I normally had a period while I was on the pill so I'm really confused as to what is going on, has anyone else had similar happen to them? 
Thank :)