Possible PMDD & Birth Control ?

I'm 18, not sexually active & currently on my second day of my period but the day before I started I was really sad. I felt extremely lonely & helpless, I kept asking my brother to sit & watch tv with me so I wouldn't feel so alone & needy. I was trying to find something happy to watch on tv but everything I watched triggered me to cry & to have self destructing thoughts. I felt extremely depressed more than usual , as if all my hidden emotions came rushing out all at once & I couldn't control them. 
I've taken self diagnosistic tests online for PMDD & they all say that I have it. I don't know if it's true or not because this was the most extreme it's been. 
Also if I were to get on birth control, which I plan to do very soon, would it help me stop feeling so down right before my period ?