Open Question: Could this be ADHD or something else?

I know it's summer but I'm horrified to go back to school because my school hate me because of my 'behavioural problems' and my lack of organisation. I apparently have the 'attention span of a goldfish' and I always start doing one things and ten seconds later I'm trying to sort something else out and have no idea what I was supposed to be doing. My family are getting annoyed because I 'act like a five year old' and am always running around. I can't sit theough long presentations or movies because I get distracted and am often told by people to sit still. Also, I'm scared to wake up every day in case I do or say something stupid and I keep thinking about suicide. The thing is, I'm scared because I know I'll be really happy in a few days/weeks and people will start getting freaked out (again). I really think something is wrong with me. My school think it's ADHD, my friends think it's bipolar disorder.