Neg. test but no period?

Ok so I really don’t know what to think about this. I’ve never skipped a period in my life, but I was supposed to get it over a week and a 1/2 ago and I still haven’t. Nothing in my diet has changed, and I’m not stressing really or anything, so I don’t know what’s up. The confusing part is, I took like 10 home pregnancy tests and they all came out negative. I don’t know what’s going on. I want to go get a blood pregnancy test, but I can’t because the only place that I know of that they do that is at the reg. doctor’s office, and I can’t go there because they need parental consent to take blood, and I’m only 17. Please help! Has this happened to anyone before? Do you think it’s possible to have all those neg. preg. tests and still be pregnant? Thanks a lot!!