Weird pains in my stomach? ?

First I was getting a sharp stabbing feeling in my upper left stomach, now my bottom right. Its been going back and forth on and off for about a week. Ive also been nauseated off and on with headaches. My stomach seems to get upset a little after ever time I eat. I have irregular peorids and took a pregnancy test which was negative. Is this just a normal thing to overlook? What does it sound Like? 10 points.