How can I tell if I have AD/HD?

I really think i have AD/HD. I am always so forgetful- I forget everything. I forget to do stuff, I forget to put things away, and I can never find any of my personal belongings. I can never focus and I spend hours on facebook. I always leave schoolwork until the last minute and I feel liek I'm never organized. I'm incredibly impatient. I can never choose a radio station. I can never dress in a timely manner. I always space out. and I'm always late, all the time. I can never fall asleep at night and I can never wake up in the morning. I even slept through my midterm exam!! that i set two alarms for. What should i do? Do I have AD/HD or am I just paranoid.