How to focus on Summer AP ignments?

I am taking 5 AP cles this school year, and 3 of them require summer work. Well, I have an incredibly hard time maintaining my self-control for more than an hour or so at a time. I have severe ADHD, and I take medicine for it, but just because I CAN focus doesn't mean that I have the will power to do so. This is a serious issue, so no smart-alec answers, please.