I have been using this online menstrual calendar and it works out my average days and all that.I had unprotected sex on the 12th april and my last period was on the 22nd march and it said i was meant to start on the 23rd april but i think i started on the 17th april it was very little blood just drops of it every now and then but then it got a little heavier as if it was the start of a period and was stil light and lasted for a day then it went back to drops every now and then it lasted for bout 3-4 days and i waited to see if my period would start on the 23rd but it didn't. I keep having weird sensations in my lower abdomen and my appetite has increased also i keep getting lower backache, dizzy spells, little headaches which i don't get during my period, feeling bloated and cramping when i aint on my period.What could this be ?