Well - the sporatic periods would be (my guess only) b/c you started and then stopped taking the pill. This will do that to your body.
Howvever, your questions about lower abdominal pains need more clarification. They could be cramping from your period, or your body trying to figure out what's going on. But did you have an abortion recently? Did you have a miscarriage? If these cramps continue, and are more painful then you are used to experiencing, I would go to your doctor's right away.
You can also start a new topic on another forum for further help. (if it has to do with abortion, my advice is to go to that specific forum, or you may face some strong felt messages here - just a head's up to you!!!!)
hope you feel better.