Long Period? Help.

I'm worried. I do have irregular periods. They usually happen a week earlier, few days late or two weeks late. There was even one instance where I didn't get it at all one month. I had unprotected sex while on my period, last Friday. I have been super stressed out. I'm 24 and in college and I did find my first gray hair a few weeks ago. I barely eat anything during the day anymore. My life is so revolved around school. I need some help. Anyone experience this?

Update: I went to gynecologist And got a Pap smear done. He also ordered me blood work which I got done at quest diagnostics for my hormones and a few other things. He also ordered me a pelvic sonogram which I didn't get done yet. 

I got my period for this month and started today and it has started out brown. I'd like to know wtf is going on with my body.