First of all I am new hear, I am a little nervous I needed answers before I persued anything.

Since I was young my teachers have always tried to tell my parents that I should be tested for having ADD, but my parents didn't believe it was a real "disease". Now I am 20 years old and just started college. I am having a horrible time focusing in class I can't ever stay involved in homework assignments. I get bored and do other things then get bored and do other things. Constantly I feel like I have a million things I need to do and can't settle down. I don't know what to do because of my age I am afraid people will think I'm just some kid making excuses.
First of all how do I talk to my parents, and second what do I do?!