What Causes Shortness Of Breath, Dizziness And Nausea With Delayed Periods?

ive been having shortness breath dizziness and nausea,its been like a week already that my period dosent come,so im just wondering what could this be.i have a baby boy and this never happend to me when i was pregnat with him, but i know every pregnacy is difrrent but i think is better askin a profecional this kind of question,why,cause i know ill get the right answer that mite respond to my consurn,