I reckon that I've always had ADHD, and as I was born three months prematurely to a drug addict, I was probably predisposed to it too.
My current symptoms (which I've always had) are:
Severe impatience;
Very impulsive;
Very disorganised;
Always late;
Always forgetting appointments and losing things;
Bad memory;
Easily distracted;
Don't complete tasks easily, especially boring ones;
Can't manage money and am a great spendthrift;
Lack of drive - just float and 'bimble' along through life;
Poor social skills but these have got much better with age - I was once very shy and socially anxious but now would consider myself quite sociable.
There are a few others but I can't think of them at the moment - maybe another ADHD symptom..?! 
Does this sound like ADHD? How would I go about getting a formal diagnosis?