11 days late, negative pregnancy test *never been on medication, birth control, or unhealthy?

I'm 29 and this is my first time ever being late for a period. I chart my period and I have a mental vibe when my period will come on. To my surprised it didn't show up! I never been on medication, birth control, never been pregnant, I'm not over weight or under weight, nor am I stressing, no change in diet etc. I'm on a 27 day cycle and my last period was Jun 13. I had sex on the 27/28 when I was very fertile, according to some charts, but it was protected (really) and neither one of us climax because we stopped really early being that I was too tired and sleepy when my s/o wanted to. I have no pregnancy symptoms. I've read many q/a on this topic but many either got off of birth control, on some medications and I was never on any. I consider myself to be healthy and I'm worried as to why my period isn't on yet. The thought of the doctors office make me queasy. Any suggestions.