How do I prevent myself from spacing out (I have ADD/ADHD)?

I'm only a 15 year old girl and I've got a serious problem. I'm tired of people making rumours up about me being on dope when I'm not. This is embarrassing and really hurts my feelings. Anytime a task becomes difficult or an everday conversation gets uninteresting, I find my mind wandering and then I'll be staring at some imaginary object in thin air. Are there any supplements, home remedies that will take away the "spacing out" for a little while, or any habits I could get into to get rid of this?