Missed period!?

It's been 2 weeks that I haven't had my period and I went to to the doctor yesterday to get checked, they told me I was not pregnant and that it might be due to stress and or a change that I've made to my body. I haven't been stressing or anything hasn't changed. I had spotting a week before missing my period and it only lasted a couple seconds once I seen it it was gone. Should I take a blood test or just wait for my period to come?