What Causes Delayed Menstruation With Dizziness And Nausea?

Hi, I am 25 years old. I've had late periods for the last couple of months. I am sexually active but not pregnant. Due to the delays, I am experiencing nausea and dizziness. It started last month and I even had a panick attack last month with some sweating. My boyfriend thinks it is hypothyroidism, because I am experiencing all of its symptoms. Even though I know my period will start soon, I know that something has changed and that this is not normal. I am feeling stressed and angry most of the time... I always had regular periods every 30-32 days. What is the matter with me? Do I need to worry?