I don't think that when I was a week late I could tell that I was pregnant but at about 6-8 weeks I had morning sickness bad enough that there was no doubt. Also about that time I noticed that my breasts were tender, like they feel right before a period. They have pregnancy tests now that can tell pretty early. I'd say give it another week and then try the test again.
Here's a site that has listed several of the early symptoms of being pregnant.
http://www.surebaby.com/