Do I have Bi-Polar disorder? Please Answer!!!!?

I'm almost 18 and the last year has been hell. I'll go from feeling ecstatic and that nothing could be better full of hope and optimism, then one little thing will go wrong or sometimes nothing will go wrong and I will get either depressed or really enraged. My self confidence goes from really high to extremely low like a roller coaster and my memory for the past year has gotten really bad ( It was really good before and I'm trying to improve it with no results. I can't remember anything from last November and before). I've thought about killing myself and I also have very strong ual feelings towards my girlfriend at some moments. Like really strong I can't think of anything else and it's ruining my life. I've done really reckless things when I'm angry like I stole my dad's car and went joy riding and when I'm angry I don't care about anything. I can do anything and not care at all about the repercussions. I go from bouts of sorrow to euphoric highs. I also have a blood relative with bi-polar disorder.