What Causes Irregular Periods With Pregnancy Symptoms?

HAD A LATE PERIOD IN APRIL CAME ON THE 6TH INSTEAD OF ON THE 2ND, HAD ANOTHER ON THE 29TH. NOT LIKE MY USUAL BLEEDING, HAD ONE AGAIN EARLY ON THE 14TH NOT LIKE USUAL CAME FOR2DAYS STOPED AND CAME FOR ONE DAY ANDSTPED, COMES WITH MENSTRUAL CRAMP. I AKE IBUPROFEN FOR THAT. HAVE BEEN HAVING OCCASSIONAL PREGNANCY SYMPTOMS LIKE NAUSEA, FOOD CRAVING, MY ABDOMEN IS BIGGER NOW AND I HAVE PUT ON WEIGHT. I WOKE UP TODAY WITH SEVERE ABDOMINAL CRAMPING BUT NO BLEEDING. SHOULD I CONTINUE TO TAKE IBUPROFEN? I DID A URINE PREGNAY TEST WHEN MY PERIOD WAS DELAYED BUT IT WAS NEGATIVE. I AM SCARED WHAT COULD BE GOING ON?