OK well my cycle is usually a 28 day cycle ever since I was 11 yrs old... last year in August I started having unprotected sex with my boyfriend and this last until the end of January of this year... my period are usually very regular and the only PMS I have are cramps the day I'm surposed to start, lower back pains a week before I'm surposed to start and 1 pimple a month... well for about 3 months now my period has been irregular, feeling nauseated, back pains, sore breast and fullnes, (which is very unsual for me) and I'm getting pimple everywhere... Plus in the 21st of January I started my period, I ovulated or was surpose to ovulate between the 8th and 12th of January.. well the day after my period I had sex and later on that night I had spotted very light pink blood and it only last for like 5 min... could that have been implantation bleeding... I'm really confused... that have never happened to me before