On the 27th April had unprotected sex but that time of month I usually come on but test was negative put it out there. On the 7th May to 10th my period" Was not normal the flow was strange it was different from the ones I usually have and this month on 5th June my period started to be watery brown/red and next day but on the 7th to now 9th June its been light red not alot but say small amount of blood with small clots. From the unprotected sex i had 2 weeks been past I've had lower back pain and bellyache pain also cramping still am but Can sex change ur menstrual cyle and mess it up? Or is this something major and need checking out by doctors?