You could be pregnant, I would get a doc to do a blood test to be sure. My body use to change it's cycle a lot, but since you are trying to conceive you should be seeing a doctor regularly.
My period was due Wednesday February 23, 2011 and my end was Sunday February 27, 2011 but last night my period started during those days I was having mild cramping to a shape pain I never had that happen before I'm not on birth controls or diet and I have been trying to have a my 4th child etc now I'm feeling like I could been pregnant I'm sitting here feeling like I lost something!!!!!
If you remember having intercourse several days or weeks after you last period, then you might be pregnant, otherwise it could just be your cycle is irregular and is trying to adjust
It sounds like to me that you are having an early miscarriage you really need to see an obgyn hope this helps!