Late period question-

Audrey
My period is about 3 days late now and I have not yet taken a pregnancy test. I keep having cramps in the morning and they usually die down by lunch time. I've been having cramps for probably 5 days now. Other than cramping, acne break out/oily skin, and fatigue I haven't really had any of the usual PMS symptoms like I typically have. I haven't really been stressed this past month and the only change I can really think that I've made is I started taking prenatal vitamins maybe two weeks ago. Any thoughts on why my period might be late? I would love to say that it's due to pregnancy but I'm so scared to get my hopes up yet...especially when I'm not really having any pregnancy symptoms. Unless cramping is one?? Not sure how long the cramping would last though. 
Thanks in advance for your input! We're currently traveling till wed and I'm waiting until we get back home before I take a test.