I would test, if only for the peace of mind. If you're unsure how late you are, you should probably start keeping a log of your periods. You can use the one here:
http://www.medhelp.org/user_trackers/gallery/menstrual or even just mark it on a calendar.
It never hurts to test!!! Well it can hurt the wallet if you are a serial tester like some of us have been. But I say go for it :)
if your prego you can feel like you are about to start...i did and i even put in a tampon thinking i probably would. i'd test :) it won't hurt and if its negative and you still don't start test again in a few days!