What Causes Delay In Menstruation Other Than Pregnancy?

Ok, I used to be able to pin point my cycle and knew my body very well. For the last 3 months, we have been trying to conceive. Last month, my period was 5 days late 2/19, pregnancy test was negative (took 3). I had cramping all that week, then it finally came and was very painful this time, it only lasted 2.5 days. There was some shedding of the lining. Since then, I have been very moody and irritable, very emotional, frequent urination, feeling bloated, today I have had heartburn all day and a dizzy spell. Could I still be pregnant or is this left over hormones from a miscarriage? Im so confused.