it depends on your age. you should have a dr do the test for you cause the can checkyourblood levels. i went without a period for almost a year,but that was because i went thru a bunch of b.c. but it came back and I got pregnant with my last child. go see your dr
There are many reasons as to why your period could be late and you're feeling like this, but pregnancy would be the go-to option. I would think back to the times you had sex around the time/right after your last period and see if there is a chance you could have gotten pregnant. At home tests aren't always reliable if your body is not producing enough of the hormone to be picked up by the test, but usually (I stress the word "usually") they would be accurate around this time.
I suggest you go to your doctor and get a blood test to find out. This way you can know if you are or not, and if you are not your doctor may be able to check for other issues that are going on.
Hope this helps!