Period 1 week late, cramps, and a negative pregnancy test

My period is one week late. Not that big of a deal, but they are usually pretty regular. Mabye only one or two days difference. So I thought I would take a test to see if I'm pregnant. I have taken two in this time period, both were negative. I am having cramping like if I was on my period. All the normal sensations and pains that I get when I'm on my period, I'm having now, except breast tenderness. I'm not under any undue stress that would delay my period. I am also having pain in my lower right side of my abdomin, a little lower then my hip bone area. I can take the negative pregnancy test, but with all the other symptoms, I'm a little confused as to the problem. The cramps are very convincing that I should be starting my period but nothin has come down. I haven't even had any spotting. I have a 4 year old. When I took my pregnancy test with him, I took it 2 days before my period was due and it showed I was pregnant before I put it down. I had a Cesarean section with him. Not sure if any of this would have anything to do with it. I just wanted to give as much info that I could. Does any of this sound like I should see a doctor? Or just keep track of all the symptoms and see what happends. I'm just sittin here frustrated and confused.