5 Days Late

Leigh
Hi. My period is five days late. The latest it's ever been is 6 days, but it's usually only a day or two late. 
I'm in a steady relationship and we have sex pretty often. We usually use condoms but sometimes we don't and he just pulls out. 
I'm seeing a nutritionist and I've been taking a bunch of new vitamins, so I'm wondering if that's effecting it.  I've also been super stressed lately. 
I'm not sure how soon I should take a test or if I should just wait. 
Help?