pregnant or effects from surgery?

I had major brain surgery on April 9th. The day I had my surgery was the last day of my last period. My period is now 7 days late. I usually spot a day or two before I get my period, and nothing so far. I am also usually very regular. I know you're cycle can be affected by stress and different medications. When I first noticed I was late I looked into seeing if having had anesthesia affected cycles and from what I read it typically does not. my husband and I have been intimate though I can't recall if it was within my ovulation window or not. I did have some cramping around the time my period should have first arrived and some light pinching feelings on the left side of my uterus as well as I have started feeling somewhat nauseous. I've noticed the last 2 times I had a McDonald's cheese burger I felt very sick afterwards and last night I could barely eat my Mac and cheese, which I ate just fine 2 weeks ago. I'm afraid to test cause every time I think I might be pregnant it comes bag negative and I just don't want to see another negative. We aren't trying to conceive, after all I just had surgery. but I wouldn't mind if I was pregnant.